Firm1  —adj. 1 a solid or compact. B fixed, stable, steady. 2 a resolute, determined. B steadfast, constant (firm belief; firm friend). 3 (of an offer etc.) Definite; not conditional. —adv. Firmly (stand firm). —v. (often foll. By up) make or become firm, secure, compact, or solid.  firmly adv. Firmness n. [latin firmus]