The term "gibbous moon" refers to the phase of the moon's cycle when more than half but less than all of the moon is illuminated by the sun, making it visible from Earth. A gibbous moon can be either waxing or waning, explains Universe Today.
The gibbous moon phase occurs twice in each complete lunar cycle. As the moon transitions from a new moon to a full moon, the moon undergoes a waxing gibbous phase prior to becoming a full moon. As the cycle reverses, the moon becomes a waning gibbous moon as it transitions from a full moon to a third quarter moon.