Using a customer supplied envelope, an individual can mail a Priority Mail Express letter envelope weighing one ounce up to sixteen ounces for $31.20 plus the extra fee of $12.50 to add Sunday/Holiday Delivery.
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).
Definition of MUSCLE for Kids. 1. : a tissue of the body consisting of long cells that can contract and produce motion. 2. : an organ of the body that is a mass of muscle tissue attached at either end (as to bones) so that it can make a body part move.. a: a body tissue consisting of long cells that contract when stimulated and produce motion b: an organ that is essentially a mass of muscle tissue attached at either end to a fixed point and that by contracting moves or checks the movement of a body part. 2.