Heisenbug

  1. n. A bug which changes its nature in accordance with an apparently chaotic set of rules when investigated, and becomes more difficult to reproduce and more damaging as the investigation continues. Name derived from the Heisenburg Uncertainty Principle.
  2. A bug which occurs only in instances so unreproducible, unlikely, or complex that users who encounter it should be offered positions in QA.
  3. A Schweitzerbug.