Green’s Dictionary of Slang

lose it v.

1. [1950s+] to lose control temporarily; in an extreme case to have an actual mental breakdown, to go mad.

2. [1970s] to lose one’s virginity.

3. [1980s+] (US campus) to be surprised, to be shocked.

4. [1980s+] (US campus) to vomit.

5. [1990s+] to lose one’s skills, abilities.

6. to pass out.