Knock 'em Dead is an expression used to describe a performance that is so impressive that it leaves the audience in awe. The crossword solutions for this term are SLAY, WOW, and BREAKALEG. SLAY is a verb meaning to kill or cause great destruction, WOW is an interjection expressing strong admiration or amazement, and BREAKALEG is an idiom meaning to do something extraordinary. Together, these words suggest that a Knock 'em Dead performance is one that is so powerful and extraordinary that it leaves the audience speechless.