The meaning of words can adequately be described using Wittgensteins concept of language games.
So while in your example people say that they "define"
- love is 'the absence of hate'
- hate is 'the absence of love
what people really do is creating/changing the meaning of words by using them.
The takeaway is that in general, words derive meaning from their usage alone, not from dictionaries defining meaning. Dictionaries follow and describe the usage of words in a culture. Dictionaries also try to make everyone agree on a meaning, but when in doubt, dictionaries have to be changed when people start using words differently.
Only in certain sciences like those based on maths do words have meanings grounded additionally in numbers instead of only in usage, making their meanings real hard to change (using them wrongly consistently). Only for such words is it useful to even speak about "definitions" of words, many words that we use don't have a "definition", they merely have a "usage guideline".
Else the mental image of meanings of words being something stable is an illusion that comes from the changes being relatively slow. Similar to the illusion that stars, continents or glaciers are non-moving, just because they move so slow.