deltoid

/ˌdɛlˈtɔɪd/

/ˈdɛltɔɪd/

Other forms: deltoids

Your deltoid is your shoulder muscle — it makes up the rounded part of your shoulder and allows you to twist, raise, and extend your arms.

When deltoid is used as an adjective, it means "triangular," so you could describe your A-frame house or pup tent as deltoid. The deltoid muscle got its name because of its triangular shape and its three distinct sections of muscle fibers. Weight lifters and body builders sometimes call these muscles "delts" for short. Deltoid comes from the Greek deltoeides, "triangular," or "shaped like the Greek letter delta."

Definitions of deltoid

1. noun

   a large triangular muscle covering the shoulder joint and serving to abduct and flex and extend and rotate the arm
   synonyms: deltoid muscle, musculus deltoideus

   type of:

   skeletal muscle, striated muscle

   a muscle that is connected at either or both ends to a bone and so move parts of the skeleton; a muscle that is characterized by transverse stripes
2. adjective

   triangular or suggesting a capital delta, with a point at the apex
   synonyms:

   simple, unsubdivided

   (botany) of leaf shapes; of leaves having no divisions or subdivisions