1. (

• leaven ,
• leavening

) a substance used to produce fermentation in dough or a liquid ;

2. (

• leaven ,
• leavening

) an influence that works subtly to lighten or modify something; "his sermons benefited from a leavening of humor" ;

1. (

• raise ,
• leaven ,
• prove

) cause to puff up with a leaven; "unleavened bread" ;