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muscle cell-an elongated contractile cell that forms the muscles of the body. muscle fiber, muscle fibre. fibre, fiber-any of several elongated, threadlike cells (especially a muscle fiber or a nerve fiber).
Freebase(0.00 / 0 votes)Rate this definition: Muscle. Muscle is a soft tissue found in most animals. Muscle cells contain protein filaments that slide past one another, producing a contraction that changes both the length and the shape of the cell. Muscles function to produce force and motion.