/ Dictionary / Index B basement membrane: Meaning and Definition of Find definitions for: base'ment mem"brane Pronunciation: [key] — Cell Biol. Cell Biol. a thin, extracellular membrane underlying epithelial tissue. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. basement complex base metal Related Content Daily Word Quiz: fidelity Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language