The Collaborative International Dictionary of English v.0.48:
Shoulder \Shoul"der\, v. t. [imp. & p. p. Shouldered; p. pr. &
vb. n. Shouldering.]
1. To push or thrust with the shoulder; to push with
violence; to jostle.
As they the earth would shoulder from her seat.
Around her numberless the rabble flowed,
Shouldering each other, crowding for a view. --Rowe.
2. To take upon the shoulder or shoulders; as, to shoulder a
basket; hence, to assume the burden or responsibility of;
as, to shoulder blame; to shoulder a debt.
As if Hercules
Or burly Atlas shouldered up their state. --Marston.
Right shoulder arms (Mil.), a position in the Manual of
Arms which the piece is placed on the right shoulder, with
the lock plate up, and the muzzle elevated and inclined to
the left, and held as in the illustration.