Covert (feather)
WordNet
adjective
(1) Secret or hidden; not openly practiced or engaged in or shown or avowed
"Covert actions by the CIA"
"Covert funding for the rebels"
(2) (of a wife) being under the protection of her husband
" a woman covert"
noun
(3) A covering that serves to conceal or shelter something
"They crouched behind the screen"
"Under cover of darkness"
(4) A flock of coots