All 3 Uses of

grotesque
in
Oryx and Crake

He doesn't want to startle them, strain their politeness, cross their boundaries without being invited — loom up on them suddenly out of the shrubbery, like some grotesque flasher exposing himself to schoolkids.†
p. 153.9

But in the time it takes him to cover the distance, slip-stepping as if in some grotesque dance with the pigoons still staring, dark clouds have come boiling up from the south, blotting out the sun.†
p. 235.9 *

They're sitting in a semi-circle around a grotesque-looking figure, a scarecrowlike effigy.†
p. 360.4

Definitions:

(1) (grotesque)
distorted and unnatural in shape or size -- especially in a disturbing way

or:

ugly, gross, or very wrong
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

More rarely, grotesque can refer to a style of art or instances of it that combines or distorts in a fanciful way natural forms into something that is often ugly or disturbing. Grotesque can also be used specifically to reference a gargoyle-like sculpture without a waterspout.