All 4 Uses

subtle
in
The Darkest Minds
(Auto-generated)

There was a subtle limp to her walk, maybe, but if I hadn't known what had happened, I would have just assumed she was coming in from a long afternoon of working in the Garden.
p. 33.8 *

subtle = not obvious, but noticeable if you look carefully
"Most people are going to have a hard enough time accepting that we're not monsters, without reports about us maiming innocent people," Clancy said. "So, please, keep spreading the black. Keep using the symbol. Just . . . try for some subtlety."
p. 358.9

subtlety = something that is not obvious, but noticeable by someone with adequate sensitivity and relevant knowledge
His shoulders were no longer bunched up with tension, and when he tilted his head toward me, I saw it for the subtle invitation it was.†
p. 255.9
It was easy enough to find the action—two hundred—odd kids gathered around a raging bonfire to eat wasn't exactly subtle.†
p. 339.4

Definitions:

(1) (subtle as in: a subtle poison)
working in an indirect or hidden way
(2) (subtle as in: a subtle shade of blue)
understated so as not to draw excess attention
(3) (subtle as in: a subtle difference or thinker)
not obvious, but noticeable with enough insight and knowledge

or:

able to notice or understand things that require insight and sensitivity
(4) (meaning too rare to warrant focus)