I. ˈdelˌtȯid noun
or del·toi·de·us ̷ ̷ˈ ̷ ̷dēəs
( plural deltoids -dz ; or deltoidei -dēˌī)
Etymology: deltoid from New Latin deltoides, from Greek deltoeidēs delta-shaped, from delta + -oeidēs -oid; deltoideus, New Latin, alteration of deltoides
: a large triangular muscle that covers the shoulder joint, serves to raise the arm laterally, arises from the upper anterior part of the outer third of the clavicle and from the acromion and spine of the scapula, and is inserted into the outer side of the middle of the shaft of the humerus
II. adjective
Etymology: New Latin deltoides, from Greek deltoeidēs
1. : shaped like a capital delta : triangular
a deltoid leaf
the deltoid muscle of the shoulder
— see leaf illustration
2. : constituting or formed like a river delta