Definition of muscle:
one of the contractile organs of the body
animal tissue consisting predominantly of contractile cells
a bully employed as a thug or bodyguard; "the drug lord had his muscleman to protect him"
authority or power or force (especially when used in a coercive way); "the senators used their muscle to get the party leader to resign"
possessing muscular strength
make one's way by force; "He muscled his way into the office"