1. departure; departing from ...; leaving at (e.g. 8:30)
九時発のバスに乗ります。I'm taking the nine o'clock bus.
2. sent from ...; (a letter, etc.) dated ...; datelined ...
3. counter for engines (on an aircraft)
4. counter for gunshots, bursts of gas, etc.; counter for bullets, bombs, etc.; counter for blows (punches); counter for jokes, puns, etc.; counter for ideas, thoughts or guesses
十二発もあれば十分でしょう。Twelve shots should be enough.
5. counter for ejaculations or sexual intercourse