Plethora definition : overabundance; excess.. See examples of PLETHORA used in a sentence. PLETHORA definition : 1. a very large amount of something, especially a larger amount than you need, want, or can deal…. Learn more. PLETHORA meaning : 1. a very large amount of something, especially a larger amount than you need, want, or can deal…. Learn more. Plethora Definition , Usage, Examples, Antonyms, Synonyms and related concepts. No need to search again - Memorize it with Dictozo