Wiktionary
sink holes
n. (plural of sink hole English)
Usage examples of "sink holes".
On the second day they walked for miles, through the ancient land where once sandblows could cover whole villages, through the old, abandoned rabbit farms, past mysterious, ever-moving sink holes.
The bogs held sink holes, the surface treacherous to those who didn't know their way through.
A rope was tied around his waist as a precaution, and twice he dropped into sink holes and had to be dragged back to the surface.
Some near the surface have caved in, leaving gaping sink holes in the land.