/ Dictionary / Index T trimethylene: Meaning and Definition of Find definitions for: tri•meth•yl•ene Pronunciation: (trī-meth'u-lēn"), [key] — n. Chem., Biochem. cyclopropane. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. trimethoprim trimethylglycine Related Content Daily Word Quiz: clairvoyant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language