Wiktionary
n. 1 (context boxing English) A coach, trainer or other assistant who attends to a boxer between rounds. 2 (context basketball English) A player who can play both the small forward and power forward positions.
Wikipedia
A cornerman, or simply corner, is a combat sports term for a coach or teammate assisting a fighter during the length of a bout. The cornerman remains outside the combat area during the fight, but in proximity, and can assist the fighter through instruction. This instruction can take place in between rounds, as in boxing.
The cornerman occasionally performs cutman duties such as applying ice to reduce swelling and stopping bleeding. The cornerman may also be responsible for throwing in the towel when necessary.
In boxing cornermen are called seconds; originally, seconds were the agents of participants in a duel.
Usage examples of "cornerman".
Wild Notes of a Weird Cornerman When I'm gone, boxing will be nothing again.
There was some halfhearted booing from the diehards who never want a fight stopped, and one of Canelli's cornermen was insisting his fighter could have gone on, but Canelli himself seemed just as happy the show was over.
Mesplede is staging weekly Cong-ARVN boxing matches (slave cornermen & referees) which helps blow off steam & boosts morale.