Green’s Dictionary of Slang

bail v.

[SE bail out, to escape from an airplane cockpit]

1. [1940s] (US black, also bail back) to enjoy oneself.

2. [1970s+] (US campus, also bail off, bale) to leave; thus bail on v.

3. [1980s+] to play truant; also in non-school/college context.

4. [1980s+] to terminate a relationship, to break up; to abandon in a non-sexual sense.

5. [1990s+] to run.

6. [1990s+] (US black) to strut, to walk in an aggressive manner.

7. [1990s+] to throw away.

8. [2000s] to back down, to abandon a promised act.

In phrases

bail in (v.)

1. [1980s+] to join in, e.g. a fight.

2. [2000s] (Irish, also bail into) to pick up.