(Homonym: wain).
1. To become smaller.
2. To decrease in phase.

1. The act or process of waning
2. A period or time of waning; specifically; the period from the full moon to the new moon
3. [Middle English, defect, from Old English wana; akin to Old English wan deficient]; a defect in lumber characterized by bark or a lack of wood at a corner or edge