Answer: POW

In the context of "POW" being a sign of a big hit, it is likely a reference to the sound effect used in comics or cartoons to represent the impact of a punch or a strike. The word "POW" is typically written in bold, capital letters within a speech bubble to emphasize the intensity of the hit. So, in this case, the word "POW" is a visual representation of a big hit or impact.

Note: The provided meaning of the answer is for the latest New York Times crossword puzzle clue: Comic book sound. Explanations are generated by AI and may be inaccurate.