Break a leg!

break a leg

A phrase of encouragement typically said to one who is about to perform before an audience, especially a theater actor. It is thought to be used due to the superstition that wishing one "good luck" will result in the opposite, but the exact origin of the phrase is unknown. You all look great in your costumes! Break a leg!
See also: break, leg
Farlex Dictionary of Idioms.

Break a leg!

Fig. Good luck! (A special theatrical way of wishing a performer good luck. Saying "good luck" is considered by actors to be a jinx.) "Break a leg!" shouted the stage manager to the heroine. Let's all go and do our best. Break a leg!
See also: break
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

break a leg!

good luck! theatrical slang
See also: break
Farlex Partner Idioms Dictionary

break a ˈleg!

(spoken) used to wish somebody good luck: You’d better leave now if you want to arrive early for the exam. Break a leg!
It is thought that wishing for something bad to happen will prevent it from happening. This expression is used especially in the theatre.
See also: break
Farlex Partner Idioms Dictionary

Break a leg!

exclam. Good luck! (A special theatrical way of wishing a performer good luck. Saying good luck is considered to be a jinx.) “Break a leg!” shouted the stage manager to the heroine.
See also: break
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • break a leg
  • (one's) best foot forward
  • best foot forward
  • Are you a man or a mouse?
  • go get 'em
  • keep the faith
  • Keep the faith baby!
  • (as) sure as eggs (is eggs)
  • this too shall pass (away)
  • give it time
References in periodicals archive
IN THE THEATER, THE CUSTOMARY WAY FOR YEARS TO WISH AN ACTOR GOOD LUCK as he makes his first appearance in a show is to pat him on the back and say, "Break a leg!"
Broken bones have impaired many a major league career. (Warm Up Tosses)