/ Dictionary / Index P position isomer: Meaning and Definition of Find definitions for: posi'tion i"somer Pronunciation: [key] — Chem. Chem. any of two or more isomers that differ only in the position occupied by a substituent. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. positioner position line Related Content Daily Word Quiz: immense Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language