Liminality (from the Latin Limen, meaning threshold) is a technical term deployed in Anthropology describing the ambiguity and disorientation which occurs in rites of passage from an 'earlier' life to a 'later' life; (commnon ones being marriage and adolescence).
It has been deployed more widely to describe political and cultural change; and
during liminal periods of all kinds, social hierarchies may be reversed or temporarily dissolved, continuity of tradition may become uncertain, and future outcomes once taken for granted may be thrown into doubt. The dissolution of order during liminality creates a fluid, malleable situation that enables new institutions and customs to become established.
Can one, then thus characterise Post-Modernity as a liminal phenomena? For the failure of grand-narratives or the master-signifier means continuity of tradition becomes uncertain (Arendt also notes this break in European Philosophy as dating from Nietzsche) but it seems that this designation can only be awarded in hindsight.