membrane āļāļ·āļāļāļ°āđāļĢ membrane āļāļ·āļāļāļ°āđāļĢ Biology A thin, pliable layer of tissue covering surfaces or separating or connecting regions, structures, or organs of an animal or a plant.Biology Cell membrane.A piece of parchment.Chemistry A thin sheet of natural or synthetic material that is permeable to substances in solution.
