beat one’s brains out—
1. (also: dash one’s brains out) kill oneself by smashing one’s head:
- There would be nothing to stop me from plunging down the well of the staircase and beating my brains out.
2. (coll.) think hard; struggle with a difficult task (also: beat one’s brains):
- I’ve been beating my brains out all day over that report.
blow one’s brains out—(coll.) kill oneself by shooting in the head:
- When his wife left him, Peter thought there was nothing left for him to do but blow his brains out.