SHOWSTOPPER

showstopper, show-stopper

(noun) something that is strikingly attractive or has great popular appeal; “she has a show-stopper of a smile”; “the brilliant orange flowers against the green foliage were a showstopper”

showstopper, show-stopper, stopper

(noun) an act so striking or impressive that the show must be delayed until the audience quiets down

Source: WordNet® 3.1

Etymology

Noun

showstopper (plural showstoppers)

A performance or segment of a theatrical production that induces a positive audience reaction strong enough to pause the production.

Any impediment that prevents all further progress; especially a software bug that must be fixed before any further development is possible.

Usage notes

Ambiguous connotation, depending on context: very good or very bad.

Source: Wiktionary