/ Dictionary / Index S semipermeable: Meaning and Definition of Find definitions for: sem•i•per•me•a•ble Pronunciation: (sem"ē-pûr'mē-u-bul, sem"ī-), [key] — adj. permeable only to certain small molecules: a semipermeable membrane. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: semipermeable (Thesaurus) semipermanent semiplastic Related Content Daily Word Quiz: procrastinate Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language