| 1. | Theater. a performer or performance that wins enthusiastic or prolonged applause. |
| 2. | a spectacularly arresting or appealing person or thing: This bright plaid suit is a real show-stopper. |

showstopper
A hardware or (especially) software bug that makes an implementation effectively unusable; one that absolutely has to be fixed before development can go on. Opposite in connotation from its original theatrical use, which refers to something stunningly *good*.
[The Jargon File]
(1995-01-31)