gusset means: A gusset panel is either triangular in shape or diamond-shaped that’s inserted into garments to shape or reinforce key areas like the underarms and crotch. Gussets are found in contemporary tights or pantyhose. They add breathability and breadth to the crotch seam. This panel is where the phrase “Don’t break a Gusset” doesn’t mean don’t tear your pants. (in Fashion Dictionary)

What else does gusset mean?

A small piece of diamond-shaped fabric is sewn to the underarm or crotch of a shirt. These are often tight fitting and can be stressed. Gussets provide additional flexibility and width. These areas have a lower likelihood of seaming torn. (in Fashion Dictionary)

Triangular inserts, such as those found in seams of garments, are used to increase strength and expansion. (in Merlin Dictionary)

Triangular bracket made of metal that is used for strengthening joists. (in Merlin Dictionary)

Protecting the joints of a suit or armor is a piece of plate armor, mail, or other type of protection. (in Merlin Dictionary)