inseam

noun

1. an inside or inner seam of a garment, especially the seam of a trouser leg that runs from the crotch down to the bottom of the leg.

adjective

2. of or relating to such a seam: inseam measurements.
3. (of a pocket) placed at or sewn to an opening in the seam of a garment, usually the side seam, so as to lie completely inside the garment.