Meaning

adjective of or relating to or consisting of muscle

adjective having a robust muscular body-build characterized by predominance of structures (bone and muscle and connective tissue) developed from the embryonic mesodermal layer

adjective having or suggesting great physical power or force

originLate 17th century; from muscle (Latin mūsculus) + -ar. Compare French musculaire.

Etymology from Wiktionary, CC BY-SA 3.0