n. Someone with a lean, only slightly muscular body
n. : Theoretical body type in which a person has a high metabolism. Such a person can easily maintain a low fat physique, but does not add muscle or body weight easily.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. a person with a thin body
Word Usage
"To fit a size 6 pair of jeans, you need narrower than average hips - an 'ectomorph' build."