be all brawn and no brain(s)

be all brawn and no brain(s)

To have great power or physical strength but lack mental acuity or intelligence. He may have been a good football player in high school, but he was all brawn and no brains, so he didn't get into any colleges.

See also: all, and, brawn, no

Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.