I was wondering that sometimes I have feelings that doesn't mean fear but when I describe that feeling to my friends they said this is fear , Can we define exact meaning for each feeling ? for example can You say what is the meaning of fear ?
1. Your use of 'exact' reminds me of the following description of structuralism in Interpretive Social Science: A Second Look. The major critique in the essay from which the following excerpt comes is the idea that we can have 'exact' understandings like the 'exact sciences' of physics, chemistry, etc.
From the interpretive point of view what is most striking about structuralism is not its difference from but its continuity with the older reductionism. That massive continuous theme is the priority and independence of logical structures and rules of inference from the contexts of ordinary understanding. As Lévi-Strauss puts it, one must avoid the "shop-grip's web of subjectivity" or the "swamps of experience" to arrive at structure and science. The ideal or "hope" of the intrinsic intelligibility of structures apart from "all sorts of extraneous elements" is the same animus that propelled the Vienna Circle. Ricoeur, in several of his essays, has drawn the clearest implications of this position. For him, the goals of structuralism can be accomplished, in fact already have been, but at a price the structuralists ignore. The conditions which make the enterprise possible—the establishment of operations and elements, and an algebra of their combinations—assure from the beginning and by definition that one is working on a body of material which is reconstituted, stopped, closed, and in a certain sense, dead. The very success of structuralism leaves behind the "understanding of action, operations and process, all of which are constitutive of meaningful discourse. Structuralism seals its formalized language off from discourse, and therefore from the human world. (12)
 See Paul Ricoeur, "Structure, Word, Event" in Conflict of Interpretations: Essays in Hermeneutics (Evanston: Northwestern University Press, 1974), 79.
2. Charles Taylor's Philosophical Arguments contains several chapters which bear on your question. You are treating language as if it is 100% descriptive, as if it merely talks about what is already there. Taylor emphasizes Johann Gottfried Herder contribution to the philosophy of language: language exhibits a constitutive element. That is, language can create reality. This is actually a common experience: by attempting to explain a topic to someone who is not an expert, one can actually come to understand it better. To view language as constitutive, interpret such an experience this way: the use of language has given additional form to the idea, changing one's conception of the idea. From Taylor:
Herder develops a quite different notion of expression. This is in the logic of a constitutive theory, as I have just described it. This tells us that language constitutes the semantic dimension, that is, possessing language enables us to relate to things in new ways, say as loci of features, and to have new emotions, goals, or relationships, as well as being responsive to issues of strong value. We might say: language transforms our world, using this last word in a clearly Heidegger-derived sense. We are talking not about the cosmos out there, which preceded us and is indifferent to us, but about the world of our involvements, including all the things they incorporate in their meaning for us. (107)
3. In contrast to structuralism, which allows for a rigorous, logical, quantitative analysis (akin to the 'exact sciences'), one can think of a more 'organic' way to understand a situation, where the result emerges from an unarticulated background which can always be further articulated (see 2.):
In this approach understanding any action is analogous to textual interpretation. This means that the intelligibility of any action requires reference to its larger context, a cultural world. So, to take a powerfully developed example, when Clifford Geertz describes the Balinese cockfight, a text analogue, he progressively incorporates other essential Balinese symbols, institutions, and practices that are necessary to an understanding of the seemingly localized cockfight. The Balinese cultural and social world is not incorporated into the cockfight, but must be brought into the analysis in order to understand the event. This is the art of interpretation. The aim is not to uncover universals or laws but rather to explicate context and world. (Interpretive Social Science, 14)
 See Clifford Geertz, "Deep Play: Notes on the Balinese Cockfight," reprinted in this volume.
4. Wittgenstein's Logical Atomism is also instructive. It is another way to look at the idea of each word having a single, definite meaning, which is sufficiently isolated from other meanings. This idea, which Wittgenstein endorsed at first, is fantastically false. Its falsity is intuitively obvious: when you look for the meaning of a word in a dictionary, and then you look for the meanings of the words used in that definition, and continue, you will ultimately 'loop back' onto previously used words. One isn't supposed to use a word to define itself, but language as a whole does exhibit this 'problem', necessarily. (Taylor talks about Wittgenstein and 'meaning atomism' in Philosophical Arguments.)
One result of this is that as you attempt to define 'fear', you will visit other words. You will realize that you could actually understand them better. In the process, you will actually understand 'fear' better. So the very attempt to define 'fear' will result in you understanding the word better. Now, will the process stop? Will you reach that perfect, all-encompassing definition? Opinions are split on the matter, but I would argue a strong no. This is probably a purely philosophical opinion, but I think one can use some sort of induction (noting its problem) to point out that there is no foreseeable limit to how much there is to understand, and how complex ideas such as 'fear' and 'love' could grow to be.
I prefer a more simplistic manner of explanation but would like to give this a shot, your endulgence is appreciated.
"Exactness" is relative in this question as meaning "exact enough" to convey the intended meaning to another. Consider the example if you ask which car a friend arrived in and they respond the "blue one" and you turn and every car in the parking lot is blue then obviously this word is not "exact enough."
So the context matters but the context is also only a tool like a word along with structure and grammer to convey meaning. In your example you give where you experience the inability to articulate your feelings in a way to convey your true meaning your question the meaning inherent in the words rather than the meaning left in people's mind.
If for example the "fear" you cannot properly convey is due to an anxiety of sorts you might describe the situation of where you have taken a test and you are about to get the results back and you have that multiplicity of feelings not accurately described as fear yet fear is a component.
So if you can conjour up in a person's mind something they can relate to subjectively then an ambiquous term such as "feeling before test results" might prove to be the more exacting words if we consider what is left in the mind after our explanation rather than what is left in the pages of a dictionary.
One could simply take one's "vorpal sword" and cut through this tangled knot with one, simple observation: No word is the thing itself.
The set of forms by which we may express anything is possibly unbounded. The particular words of one particular language are only loosely bounded, for the meanings tend to change with use, particularly the most common words.
Definitions, as in strict dictionary definitions, are themselves moving targets.
In the end, we must ask, "When I use this word, how is it understood by others, here, now?
So, again, the word is never the thing itself, by definition :) even, they are "re-presentations," and thus subject to many, many fallacies.