Can mean several things, usually related to losing control. Context is crucial:
- 1. Lose one's temper: To become suddenly and uncontrollably angry.
- 2. Become mentally unstable: To lose one's sanity or composure, often under pressure; to have a breakdown.
- 3. Burst out laughing uncontrollably: To find something so funny that one cannot stop laughing.
- 4. (Less common) Forget something important: I had the answer, but I lost it.