WordWeb Online

1. An influence that works subtly to lighten or modify something
   "his sermons benefited from a leavening of humour";
   - leaven
    
2. A substance used to produce fermentation in dough or a liquid
   - leaven

1. Cause to puff up with a leaven
   - raise, prove

Derived forms: leavenings

Type of: bring up, elevate, get up, imponderable, lift, raise, substance

Encyclopedia: Leavening, North Yorkshire