Meaning of “brace” - Learner’s Dictionary

brace

noun [ C ] uk us /breɪs/
SUPPORT

something that supports or holds something in the correct position:

He wore a neck brace for months after the accident.
TEETH

UK (US braces) a wire object that some children wear to make their teeth straight

(Definition of “brace noun” from the Cambridge Learner’s Dictionary © Cambridge University Press)