Real Dictionary

shoulder
Your shoulders are between your neck and the tops of your arms.

shoulder in American English
the joint connecting the arm or forelimb with the body
to push or thrust along or through, with or as with the shoulder
noun: the part of each side of the body in humans, at the top of the trunk, extending from each side of the base of the neck to the region where the arm articulates with the trunk

shoulder in British English
noun: the part of the vertebrate body where the arm or a corresponding forelimb joins the trunk: the pectoral girdle and associated structures

shoulder in Mechanical Engineering
noun: A shoulder is a large projection or a part of something where the shape or diameter changes suddenly, designed to withstand thrust.