资料来源 : Webster's Revised Unabridged Dictionary (1913)

Nad \Nad\, Nadde \Nad"de\ [Contr. fr. ne hadde.]
   Had not. [Obs.] --Chaucer.

资料来源 : WordNet®

NAD
     n : a coenzyme present in most living cells and derived from the
         B vitamin nicotinic acid; serves as a reductant in
         various metabolic processes [syn: {nicotinamide adenine
         dinucleotide}]