WordNet sense 1 (celebration in the Roman Catholic Church of the Virgin Mary's being taken up into heaven when her earthly life ended; corresponds to the Dormition in the Eastern Orthodox church):

Assumption of Mary

WordNet sense 2 (a statement that is assumed to be true and from which a conclusion can be drawn):

premise, premiss, premise

WordNet sense 3 (a hypothesis that is taken for granted):

supposition, supposal

WordNet sense 4 (audacious (even arrogant) behavior that you have no right to):

effrontery, presumption, presumptuousness

WordNet sense 5 (the act of taking possession of or power over something):

laying claim