(n.) A circular hole formed in the rocky beds of rivers by the grinding action of stones or gravel whirled round by the water in what was at first a natural depression of the rock.

CAT abase abasement ability aerospace aerosphere air hole air pocket airspace appulse aptness assassinate assault bang bang into bear bear upon bearing bent bilge blain bleb blister blob blow bob bobble boil boost boot boss bounce bow break brunt bubble buck buffet bulb bulge bull bulla bulldoze bulldozing bulling bump against bump into bump off bunch bunion bunt burl burst bust butt butt against button cahot caliber can cannon capability capacity carambole carbuncle carom carom into cashier casting down ceiling chance chatter chine chink chuckhole clap clash click clink clop clump clunk collide collision colophon come across come into collision concavity concuss concussion condyle confront each other convex convexity corn crack crack up crack-up cram crash crash into crosswind crowd crump crunch cyst dactylogram dactylograph dash into debase debasement defrock degradation degrade degrading dement demote demotion dent deplume depluming depose deprive destroy didder dig dilatation dilation dint disbar discharge disemploy disgrade disgrading dismiss dispatch displace displume displuming distension dither do away with do in dowel dower downgrade downgrading dowry drive drum out dull thud ear edema elbow eliminate embossment empty space encounter endowment equipment excrescence execute expel faculty fall foul of falter favorable wind fingerprint fire flair flange flap flick flop flump fog footmark footprint footstep force forte fossil footprint foul front furlough furuncle gall genius gift give the ax give the gate gnarl goad grimace hammering handle have an ague head head wind high-pressure area hill hit hit against hole humble humbling hump hunch hurt hurtle hustle ice ichnite ichnolite impact impinge impingement impress impression imprint indent indentation indention instinct intumescence ionosphere jab jactitate jam jar jerk jetstream jig jigget jiggle jog joggle jolt jostle jounce jump kick kick upstairs kill knack knob knock knock against knot knur knurl lay off let go let out