noun. a person with a thin body.
1. Noun, singular or mass If you're an ectomorph, take a short break and then do a second set. 2. Adjective If you are overweight to begin with, have bad habits such as drinking alcohol or smoking, or have an ectomorph body make-up, it might take a few more months to initially begin to see results. 3. Foreign word You may have heard the terms endomorph, ectomorph and mesomorph.