leaven

1 leaven /ˈlɛvən/ noun
1 leaven
/ˈlɛvən/
noun
Britannica Dictionary definition of LEAVEN
[noncount]
1 
: a substance (such as yeast) that makes dough rise and become light before it is baked
— called also leavening
2 
literary : something that makes a situation or mood less serious
2 leaven /ˈlɛvən/ verb
leavens; leavened; leavening
2 leaven
/ˈlɛvən/
verb
leavens; leavened; leavening
Britannica Dictionary definition of LEAVEN
[+ object]
1 
formal : to make (something) less serious and often more exciting
2 
: to add leaven to (bread, dough, etc.)