Brainless/ˈbreɪnləs/ Definition 1 of 1Pro Tip 1/3Colloquial Usage Used in casual conversation rather than in formal speech or writing. Calling his idea brainless upset everyone at the party. Pro Tip 2/3Negative Connotation Expresses disapproval or criticism, may offend if used carelessly. Her brainless remarks during the meeting didn't win her any fans. Pro Tip 3/3Metaphorical Not literal; doesn't mean lacking a brain, but lacking thought or intelligence. Don't be brainless, think before you act!