Malodorous means having a bad smell, an unpleasant odor that makes you want to hold your nose or step away. The word comes from Latin roots: mal meaning bad and odor meaning smell.

A gym locker room after practice might be malodorous from sweaty clothes and shoes. A garbage can left in the sun becomes malodorous as food waste spoils. A science experiment involving sulfur compounds could fill a classroom with malodorous fumes that send everyone rushing to open windows.

The word sounds formal and scientific, which is exactly how it's used. Scientists might describe a malodorous chemical, or a reporter might write about a malodorous canal in need of cleanup. You probably wouldn't say “that sandwich is malodorous” at lunch; you'd just say it smells bad or gross. But malodorous is perfect when you want to sound precise and objective about something that really stinks.

The opposite is fragrant or aromatic, words that describe pleasant smells like fresh bread or flowers.