have a glass jaw

have a glass jaw

Fig. to be susceptible to a knockout when struck on the head. (Said only of boxers who are frequently knocked down by a blow to the head.) When the prizefighter was knocked out cold by a right to the chin in the first round, the newspapers said he had a glass jaw. Once a fighter has a glass jaw, he's finished as a boxer.
See also: glass, have, jaw
References in periodicals archive ?
He was asked if I have a glass jaw and he said 'what are you talking about, I spar with him and he's knocked lots of sparring partners out who are heavier'.