"BirdsOfaFeather" session. More-or-less informal sessions at conferences where people with common interests can get together to chat, share experiences, and ask questions. Sometimes they take on a more formal tone, with a presenter holding forth on some topic, but the best are still the informal sessions.
French slang, it means you don't like very much:
Example:
Do you like this movie?
Bof (not really)
Beginning of File (am I showing my age?!) Nah, I had the same thought, and I'm certainly not old, nope...