noun. a large triangular muscle covering the shoulder joint and serving to abduct and flex and extend and rotate the arm.
adjective. triangular or suggesting a capital delta, with a point at the apex.
1. Noun, singular or mass The anterior deltoid is at the front of your shoulder. 2. Adjective Because the deltoid muscle is responsible for lifting the arm straight up from the side, it may be difficult or impossible to move the arm in this way.
