waning
1. [ noun ] a gradual decrease in magnitude or extent
Examples:

"the waning of his enthusiasm was obvious" "the waxing and waning of the moon"

Related terms: waxing decrease wane
2. [ adjective ] (of the moon) pertaining to the period during which the visible surface of the moon decreases
Examples:

"after full moon comes the waning moon"

Related terms: waxing
Similar spelling:   weaning