mem·brane (m?m?br?n?)n.1. Biology a. A thin, pliable layer of tissue covering surfaces or separating or connecting regions, structures, or organs of a living organism.b. A semipermeable layer that bounds a cell or an organelle, typically consisting of lipids and proteins.2. A thin, pliable sheet or layer of natural or synthetic material: the resonating membrane of a kazoo.3. A piece of parchment.4. Chemistry A thin sheet of natural or synthetic material that is permeable to substances in solution.[Latin membr?na, skin, from membrum, member of the body.]mem?bra·nal (-br?-n?l) adj.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.membrane (?m?mbre?n) n1. any thin pliable sheet of material2. (Biology) a pliable sheetlike usually fibrous tissue that covers, lines, or connects plant and animal organs or cells3. (Biology) biology a double layer of lipid, containing some proteins, that surrounds biological cells and some of their internal structures4. (Atomic Physics) physics a two-dimensional entity postulated as a fundamental constituent of matter in superstring theories of particle physics5. (Historical Terms) a skin of parchment forming part of a roll[C16: from Latin membr?na skin covering a part of the body, from membrum member]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014mem?brane (?m?m bre?n) n. 1. a thin, pliable sheet or layer of animal or vegetable tissue, serving to line an organ, connect parts, etc. 2. any thin, pliable material used as a filter, separator, resonator, etc. [1375?1425; late Middle English; Middle English membraan parchment