/ Dictionary / Index S STP: Meaning and Definition of Find definitions for: STP Pronunciation: [key] See STP Pronunciation: [key] — Slang. Slang. a potent long-acting hallucinogen. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: stp (Thesaurus) stowp St. Paul Related Content Daily Word Quiz: spectral Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language