Other forms: underwhelming; underwhelmed; underwhelms
When something underwhelms, it's not quite as great as it was expected to be. After months of waiting for a new restaurant to open, it's disappointing if the food turns out to underwhelm you.
Anything that's a letdown after some kind of excited anticipation tends to underwhelm. You might be underwhelmed by finally getting a pet after begging your parents for months — especially if it's a lizard that just sits there and stares at you. And if a new movie underwhelms all your friends, not living up to its thrilling trailers, you're less likely to go see it yourself. Underwhelm was jokingly coined in the 1950s, modeled on its antonym, overwhelm.