All 3 Uses

covert
in
Another Country
(Auto-generated)

The Negro couples were in earnest conversation—the elderly Negro woman leaned forward with great vehemence; and the three youths were giggling and covertly watching the dark man and the pasty girl; and if this evening ended as all the others had, they would presently drive off to some haven and watch each other masturbate.†
p. 295.5
She looked, covertly, at him again—her guilt began.†
p. 366.6 *
And he was, indeed, beginning to attract a certain, covert attention; he did not look American, exactly: they were wondering how to place him.†
p. 248.9

Definitions:

(1) (covert as in: a covert plan)
done in a secret or hidden way
(2) (meaning too rare to warrant focus)
Much more rarely, covert is used as a noun to describe a hidden or sheltered place. Coverts can refer to the small feathers that cover the base of a bird's flight feathers.