it's not a bug, it's a feature

Meanings

1. What one user may consider a software bug, other users may consider to be a useful feature or an intentional consequence of the system's design.
2. A self-deprecating response when confronted by a bug in the software that one is authored or is introducing to another user.
3. Affirms the validity of a counterintuitive behavior within a system; it is by design.

Etymology

Coined by American computer programmer Sandra Lee Harris in 1971 at Digital Equipment Corporation.