Resistant to externally applied pressure. Marked by or indicating the tone and resiliency of healthy tissue: firm muscles. Securely fixed in place: Despite being hit by the car, the post was still firm. Indicating or possessed of determination or resolution: a firm voice. Constant; steadfast: a firm ally. Not subject to change; fixed and definite: a firm bargain; a firm offer. Unfluctuating; steady: Stock prices are still firm. Strong and sure: a firm grasp. To make or become firm. Often used with up. Without wavering; resolutely: stand firm. A commercial partnership of two or more persons, especially when unincorporated. The name or designation under which a company transacts business.