A feather or plume, or feather-shaped item, used as an adornment or ornament.
The lesser white heron.
The feathery crown of some seeds (such as the dandelion).
Used other than figuratively or idiomatically: see feather, cap.
An accomplishment; particularly one that is flaunted or boasted of.
He thinks it is quite a feather in his cap that he figured it out for himself.