as·sume / əˈsoōm/ • v. [tr.] 1. suppose to be the case, without proof: you're afraid of what people are going to assume about me.2. take or begin to have (power or responsibility). ∎ seize (power or control): the rebels assumed control of the capital.3. take on (a specified quality, appearance, or extent): militant activity had assumed epidemic proportions. ∎ adopt falsely: Oliver assumed an expression of penitence | [as adj.] (assumed) a man living under an assumed name. DERIVATIVES: as·sum·ed·ly / -midlē/ adv.