a taking to or upon oneself. the act of laying claim to or taking possession of something. an assuming that something is true. a fact or statement (such as a proposition, axiom (see AXIOM sense 2), postulate, or notion) taken for granted. the taking up of a person into heaven. August 15 observed in commemoration of the Assumption of the Virgin Mary. the taking over of another's debts. ARROGANCE, PRETENSION.