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Webster 1913 Edition

Noun.

The act of making light, or causing to ferment, by means of leaven.

That which leavens or makes light.

Bacon.

ppr.

lev'ening. Making light by fermentation.

Noun.

lev'ening. that which leavens or makes light.

leavening ‎(not comparable)

leavening ‎(plural leavenings)