Gusset

A small piece of cloth inserted in a garment, for the purpose of strengthening some part or giving it a tapering enlargement.

Anything resembling a gusset in a garment

A small piece of chain mail at the openings of the joints beneath the arms.

A kind of bracket, or angular piece of iron, fastened in the angles of a structure to give strength or stiffness; esp., the part joining the barrel and the fire box of a locomotive boiler.

An abatement or mark of dishonor in a coat of arms, resembling a gusset.