deltoid

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A thick triangular muscle covering the shoulder joint, used to raise the arm from the side.
• adjective Triangular.
• adjective Having the shape of a geometric kite.
• adjective Of or relating to the deltoid.

from The Century Dictionary.

• noun In zoology, a deltoid plate.
• noun In mathematics, a symmetrical quadrilateral with a diagonal as axis.
• Resembling the Greek letter Δ; triangular.
• Specifically— In anatomy:
• Forming a triangular place or part; being triangular: as, the deltoid muscle.
• Relating to the deltoid muscle: as, the deltoid crest of the humerus.
• In entomology, pertaining to or resembling the pyralid moths, or Deltoides.
• In botany, triangular or trowel-shaped: as, a deltoid leaf: also applied to the cross-section of a leaf, etc.
• noun The large, coarse-fibered, triangular muscle of the shoulder, covering and protecting the joint, arising from the spine of the scapula, the acromion, and the clavicle, and inserted into the deltoid crest of the humerus. Its action raises the arm away from the side of the body. See cut under muscle.

from the GNU version of the Collaborative International Dictionary of English.

• noun the deltoid muscle.
• adjective Shaped like the Greek Δ (delta); delta-shaped; triangular.
• adjective (Bot.) a leaf in the form of a triangle with the stem inserted at the middle of the base.
• adjective (Anat.) a large triangular muscle covering the shoulder joint, which serves to raise the arm directly upward.
• adjective of or pertaining to the deltoid muscle.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The deltoid muscle, a triangular muscle on the human shoulder.
• noun The deltoid ligament, a triangular ligament on the human ankle.
• adjective In the shape of the upper case Greek letter delta Δ; triangular.
• adjective Of, or connected with the deltoid muscle
• adjective botany, of leaves Of a triangular or roughly triangular shape and attached to the stem via the side.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective triangular or suggesting a capital delta, with a point at the apex
• noun a large triangular muscle covering the shoulder joint and serving to abduct and flex and extend and rotate the arm