noun
bare shoulder; one shoulder exposed
Refers to a shoulder left uncovered, often in the context of clothing slipping off or being deliberately bared. Commonly appears in set phrases like 片肌脱ぐ (to lend a hand, literally 'to bare one shoulder').
浴衣の片肌がはだけていた。
One shoulder of her yukata was slipped off.
彼は片肌脱いで仕事を手伝った。
He pitched in and helped with the work (literally, bared one shoulder).