Pronunciation: (mol'u-kyOOl"), [key]
1. Chem., Physics.the smallest physical unit of an element or compound, consisting of one or more like atoms in an element and two or more different atoms in a compound.
2. Chem.a quantity of a substance, the weight of which, measured in any chosen unit, is numerically equal to the molecular weight; gram molecule.
3. any very small particle.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.