'To square one's shoulders' definitions:

Definition of 'To square one's shoulders'

From: GCIDE

Square \Square\, v. t. [imp. & p. p. Squared (skw[^a]rd); p. pr. & vb. n. Squaring.] [Cf. OF. escarrer, esquarrer. See Square, n.]
1. To form with four equal sides and four right angles. --Spenser. [1913 Webster]
2. To form with right angles and straight lines, or flat surfaces; as, to square masons' work. [1913 Webster]
3. To compare with, or reduce to, any given measure or standard. --Shak. [1913 Webster]
4. To adjust; to regulate; to mold; to shape; to fit; as, to square our actions by the opinions of others. [1913 Webster]
Square my trial To my proportioned strength. --Milton. [1913 Webster]
5. To make even, so as to leave no remainder or difference; to balance; as, to square accounts. [1913 Webster]
6. (Math.) To multiply by itself; as, to square a number or a quantity. [1913 Webster]
7. (Astrol.) To hold a quartile position respecting. [1913 Webster]
The icy Goat and Crab that square the Scales. --Creech. [1913 Webster]
8. (Naut.) To place at right angles with the keel; as, to square the yards. [1913 Webster]
To square one's shoulders, to raise the shoulders so as to give them a square appearance, -- a movement expressing contempt or dislike. --Sir W. Scott.
To square the circle (Math.), to determine the exact contents of a circle in square measure. The solution of this famous problem is now generally admitted to be impossible. [1913 Webster]