What moon phase is described as "about to become or just was a full moon"?

The description of a moon phase that is "about to become or just was a full moon" refers to the gibbous phase. During the gibbous phase, the moon appears more than half illuminated but not completely full, indicating its position in the lunar cycle. This phase occurs both in the waxy gibbous (before full moon) and waning gibbous (after full moon) stages.

The key aspect of a gibbous moon is that it visually suggests proximity to the full moon state, where the moon is fully lit. As the moon transitions from a full moon, it enters the waning gibbous phase, and just before it reaches full moon, it is in the waxing gibbous phase. Each of these points in the gibbous phase signifies the moon's appearance as it approaches or has just passed fullness.