Refers to a person's physical height or build, often used in descriptions of appearance.
He is tall and looks like a model.
He is short in stature but has a strong presence.
Compound of 上 (うわ, 'upper') and 背 (ぜい, 'back' or 'stature'). The reading ぜい is a rendaku form of せ. The word refers to the upper part of the body's height.