Pronunciation: (u-sOOm'),[key] —v.t.,-sumed, -sum•ing. 1. to take for granted or without proof; suppose; postulate; posit: to assume that everyone wants peace. 2. to take upon oneself; undertake: to assume an obligation. 3. to take over the duties or responsibilities of: to assume the office of treasurer. 4. to take on (a particular character, quality, mode of life, etc.); adopt: He assumed the style of an aggressive go-getter. 5. to take on; be invested or endowed with: The situation assumed a threatening character. 6. to pretend to have or be; feign: to assume a humble manner. 7. to appropriate or arrogate; seize; usurp: to assume a right to oneself; to assume control. 8. to take upon oneself (the debts or obligations of another).
9. Archaic.to take into relation or association; adopt.