The word "blab" means to reveal a secret or to divulge information that was meant to be kept confidential. In the context of the clue "Let the cat out of the bag," it suggests that someone has let a secret slip or has unintentionally revealed something that should have been kept private.
Note: The provided meaning of the answer is for the latest New York Times crossword puzzle clue: Let the cat out of the bag. Explanations are generated by AI and may be inaccurate.