gusset

Short definition from Wiktionary

Noun

1. 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. 2
   A gousset, a piece of mail providing protection where armor plates meet.
3. 3
   A kind of bracket, or angular part, 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.
4. 4
   An ordinary on a coat of arms, resembling a gusset (see usage notes).
5. 5
   A large flat metal piece wider than the valley to help prevent build-up at the base of the valley, either from debris or ice dam formations.
6. 6
   An intercellular space at an angle where more than two cells meet.

Verb

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