GUSSET

noun

1. A small piece of cloth inserted in a garment, for the purpose of strengthening some part or giving it a tapering enlargement cf. godet.
2. A small piece of mail, providing some protection where two plates of armor are joined, usually at the elbows, under the shoulders, and behind the knees.
3. (machinery) A kind of bracket, or angular piece of iron, fastened in the angles of a structure to give strength or stiffness; especially, the part joining the barrel and the fire box of a locomotive boiler.

verb

1. To make with a gusset; to sew a gusset into.