medium built 中等身材
average height中等身材
middle height
例句：
My father is of middle height. He is stout and strong. with a severe look on his face and with keen expressive eyes.
我的父親中等身材，長得結實強壯，有壹副挺嚴肅的神情和壹雙銳利而富於表情的眼睛。
He was a man of medium height with a slight paunch. His eyes shone with joy. At one look, you could instantly tell he was one of us, that is, a Mediterranean type.
他是個中等身材的人，大腹便便，眼睛裏閃爍著喜悅，妳壹眼就可看出他是我們中的壹員，即地中海人種。
還有壹種是medium size.