/ Dictionary / Index B borax pentahydrate: Meaning and Definition of Find definitions for: bo'rax pentahy'drate Pronunciation: [key] — Chem. Chem. a white, crystalline, water-soluble solid, NaBO&multiplydot;5HO, used chiefly for killing weeds, as a water softener, and as a disinfectant and deodorizing agent. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. borax bead borazine Related Content Daily Word Quiz: careening Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language