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.
  1. of or relating to such a seam: inseam measurements.
  2. (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.

Origin of inseam

First recorded in 1905–10; in-1 + seam Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018