The phrase "unpleasant smell" means a bad or disagreeable odor that is not nice to smell.
Sentences with «unpleasant smell»
This smell can kill unpleasant smells of (unhealthy) teeth, sweat and also more pleasant to many than the odor of bubble gum or cucumber water. (politics.stackexchange.com)
You need to change your hamster's bedding frequently to avoid unpleasant smells. (wikihow.com)
This oil diffuser will help mask the odors of the kitchen, pets, or other unpleasant smells. (heavy.com)