The Collaborative International Dictionary of English v.0.48:

Yeasty \Yeast"y\, a.
   Frothy; foamy; spumy, like yeast.
   [1913 Webster]

WordNet (r) 3.0 (2006):

yeasty
    adj 1: of or resembling or containing yeast [syn: yeasty,
           yeastlike]
    2: marked by spirited enjoyment [syn: zestful, yeasty,
       zesty, barmy]
    3: exuberantly creative