\As*sump"sit\ (?; 215), n. [L., he undertook, pret. of
L. assumere. See {Assume}.] (Law)
(a) A promise or undertaking, founded on a consideration.
    This promise may be oral or in writing not under seal. It
    may be express or implied.
(b) An action to recover damages for a breach or
    nonperformance of a contract or promise, express or
    implied, oral or in writing not under seal. Common or
    indebitatus assumpsit is brought for the most part on an
    implied promise. Special assumpsit is founded on an
    express promise or undertaking. --Wharton.