gib·bous 
(g
ĭb
əs)
adj.1. a. Characterized by convexity; protuberant: a gibbous seashell.
b. More than half but less than fully illuminated from the point of view of an observer. Used of phases of the moon or the planets.
2. Archaic Having a hump; humpbacked.
[Middle English, bulging, from Late Latin gibbōsus, hunch-backed, from Latin gibbus, hump.]
gibbous·ly adv.
gibbous·ness n.