Definitions:

1. to expel from a community or group verb
   • The rest of the neighborhood would like to blackball you due to the massive stink coming from your house.
2. to vote against verb
   • I blackballed your proposal because it was legitimately the worst idea I've ever heard before.

Synonyms:

• ban
• banish
• barring
• cast out
• negative
• ostracise
• ostracize
• shun
• turn thumbs down
• veto
• vote down