Wiktionary
a. (context astronomy English) More than half full in phase, but growing smaller.
Usage examples of "waning gibbous".
It was night, and the waning gibbous moon laid bare the bones of the stone circle and the long horizon of grass, a pale silver expanse under moonlight.
The waning gibbous moon rode low in the west, and its light made the road gleam as though an enchanter's hand had laid that light down before them to make their way easy—.
In the east, a waning gibbous moon, just two days past full, was rising.
Math, a day past first quarter, and mottled Tiwaz, now nearly full, jumped in and out of sight, and a couple of hours before midnight dim Nothos' waning gibbous disc joined them.
When he came at last to the edge of the clearing and looked out over the old ruins, he thought for an instant that the waning gibbous moon had splintered into two moons and that its other half burned in the ruins,attended by brilliant Seirios, the star known to navigators as the Burning Arrow.
Only the waning gibbous moon looked down at him from low in the west.