blow someone's brains out

verb2

1. •
   (slang) To shoot someone in the head.

   • [F]or Moody, on this Occasion, took a large Glass from him, and threatned to blow his Brains out, (a favourite Phrase with these Pyrates) if he muttered at it. — 1724
2. •
   (vulgar) To perform fellatio on another person, as to give them an orgasmic experience.