1. yeast - Noun
2. yeast - Verb
3. Yeast - Proper noun
The foam, or troth (top yeast), or the sediment (bottom yeast), of beer or other in fermentation, which contains the yeast plant or its spores, and under certain conditions produces fermentation in saccharine or farinaceous substances; a preparation used for raising dough for bread or cakes, and making it light and puffy; barm; ferment.
Spume, or foam, of water.
A form of fungus which grows as indvidual rounded cells, rather than in a mycelium, and reproduces by budding; esp. members of the orders Endomycetales and Moniliales. Some fungi may grow both as a yeast or as a mycelium, depending on the conditions of growth.
Source: Webster's dictionaryYou can't just leave out one part; the bread won't rise if the yeast isn't there. Holly Near
A bad act done will fester and create in its own way. It's not only goodness that creates. Bad things create. They have their own yeast. Dennis Potter
Enthusiasm is the yeast that raises the dough. Paul J. Meyer
My aim is to agitate and disturb people. I'm not selling bread; I'm selling yeast. Miguel de Unamuno
Enthusiasm is the yeast that makes your hopes shine to the stars. Enthusiasm is the sparkle in your eyes, the swing in your gait. The grip of your hand, the irresistible surge of will and energy to execute your ideas. Henry Ford
Note, that yeast of good Beer, is better then that of Ale. Kenelm Digby