/ Dictionary / Index B base unit: Meaning and Definition of Find definitions for: base' u'nit Pronunciation: [key] — Physics. Physics. one of the units, as mass, length, time, or electric current, taken as a basis for a system of units in the sciences. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. base tenant bash Related Content Daily Word Quiz: secular Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language