1.NounAny of the about 250 species of flowering plant of the genus Nepeta, family Lamiaceae, certain of which are said to have medicinal qualities.
2.NounNepeta cataria and Nepeta grandiflora (and perhaps other species), which are well-known for causing an apparently harmless pheromone-based intoxication among certain cats.
"Some cats go bonkers over catnip; others ignore it."
3.NounSomething that causes excitement or interest.