1. A tissue that can undergo repeated contraction and relaxation, so that it is able to produce movement of body parts, maintain tension, or pump fluids within the body.

There are three types: voluntary striped muscle, involuntary smooth muscle, and branched or heart muscle.

2. An organ composed of bundles or sheets of muscle tissue, bound together with connective tissue and with tendons by which the contracting part is attached to the bones that it moves.
3. Power and influence, especially in the political, financial, or military spheres.
4. Physical strength; that is, "put some muscle into it".
5. Slang: men who are employed to intimidate, harm, or menace people.
6. To move using strength and force or effort, or to make someone or something move in this way.
7. Etymology: via French, from Latin musculus, literally "small mouse" from mus, "mouse"; from the supposed resemblance of some muscles to mice.

One of a large group of muscles in the front of the abdomen that assists in maintaining regular breathing movements, supports the muscles of the spine while lifting, and which keeps abdominal organs in place: Abdominal muscles, informally known as the "abs", are the target of many exercises, such as sit-ups.

A muscle whose fibers are inserted on two sides of a central tendon.

An extension of the internal oblique abdominal muscle over the spermatic cord and testis.

The cremaster muscle covers the testis. Its function is to raise and lower the scrotum in order to regulate the temperature of the testis and promote spermatogenesis. In a cool environment the cremaster draws the testis closer to the body preventing heat loss, while when it is warmer the cremaster relaxes allowing the testis to cool.

The cremaster develops to its full extent only in males; in females it is represented by only a few muscle loops.

A large, thick triangular muscle that covers the shoulder joint: The deltoid muscle is the prime mover of the arm away from the central turning part of the body and it is also a synergist (working in combination with something else to increase its activity) of arm flexion (process of bending or the state of being bent), extension, and medial and lateral rotations.

A reference to a large, thick triangular muscle which covers the shoulder joint: The deltoideus muscles are the primary movers of arm flexions, extensions, and medial and lateral rotations.

A therapeutic electric current used to stimulate a muscle directly; such as, when the muscle is denervated (loss of nerve impulses) and peripheral nerves are not functioning.

A pathological condition of the extraocular muscles of one or both eyes.

It causes the eyes to be misaligned in one or more axes or direction.

1. A small, thin, deep muscle of the abdomen which is a diagonally arranged abdominal muscle on either side of the torso: The internal abdominal oblique muscle runs diagonally opposite and underneath the external oblique.

The internal abdominal oblique muscle has a quadrilateral form originating from the hip bone, the crest of the ilium, and extending to the cartilage of the lower ribs which are the tenth, eleventh, and twelfth ribs.

It is innervated by the lower thoracic nerves and supplies the intercostal and lumbar arteries and this muscle protects a weak point in the abdominal wall and works with the external oblique to help twist the torso.

2. One of a pair of anterolateral muscles of the abdomen, which are in front and away from the midline, lying under the external oblique muscle in the lateral and ventral part of the abdominal wall; The internal abdominal oblique muscle is smaller and thinner than the external oblique muscle and it functions to compress the abdominal contents and assists in micturition, defecation, emesis, parturition, and forced expiration.

Both muscles acting together serve to flex the vertebral column, drawing the costal cartilages toward the pubis. One side acting alone bends the vertebral column laterally and rotates it, drawing the shoulder of the opposite side downward.

In anatomy, any of several muscles enabling the thumb to be moved toward a finger of the same hand: After slipping and falling on the icy sidewalk, Gary could not use his opponent muscles to move the thumb on his right hand.

Any of several muscles of the upper back that help move the shoulder blade.

Any of three muscles on each side of the neck that serve to bend and rotate the neck and that assist breathing by raising or fixing the first two ribs.

The largest structure that is composed of bundles of specialized cells which are capable of contractions and relaxations to create movements: "The skeletal muscles, or voluntary muscles, of the body consist of more than 600 types."

"Skeletal muscles are composed of groups of muscle fibers in a systematic arrangement."

"Movements of the skeletal muscles are controlled by the brain because each muscle fiber is supplied with a nerve ending which receives impulses from the brain."

A broad, flat muscle of the abdomen with transverse fibers that is named after the direction of its fibers.

This muscle lies just below the internal oblique, originating from the lumbar fascia, iliac crest, and inguinal ligament.

It spans the area from the pelvis to the abdomen and inserts in the xiphoid cartilage and linea alba.

The transversus abdominis is innervated by the lower thoracic nerves and supplied by the lumbar arteries and this muscle assists in breathing.

Brief clarifications of the above terms as shown in bold words

• transverse fibers: the thin threadlike pieces found in body tissues that form the nerves and muscles extending or lying across bodily parts.
• internal oblique: a slanting, small, thin, deep muscle of the abdomen.
• lumbar fascia: back layer of loose tissue just beneath the skin.
• iliac crest: hip bone.
• inguinal: part of the groin where the abdomen and thighs meet.
• ligament: inelastic white materials which surround the joints, and connect bones, or strengthen the attachments of various organs, or keep them together.
• xiphoid cartilage: bottom part of the breastbone which is firm with very elastic tough tissue.
• linea alba: "white line", a fibrous band running vertically the entire length of the center of the anterior abdominal wall, receiving the attachments of the oblique and transverse abdominal muscles.

Smooth or involuntary tendons that function to produce movements as parts of the body: The visceral muscles consist of fibers which move the internal organs; such as, the digestive tract, blood vessels, and the ducts leading from the glands.

No one has any conscious control over the visceral muscles.

While the skeletal muscle fibers are arranged in bundles, the smooth visceral muscle forms sheets of fibers as it wraps around tubes and vessels.