One of a pair of long straps (usually connected to the bit or the headpiece) used to control a horse.

Roget 45: vinculum, link; connective, connection; junction etc. 43; bond of union, copula, hyphen, intermedium^†; bracket; bridge, stepping-stone, isthmus.    bond, tendon, tendril; fiber; cord, cordage; riband, ribbon, rope, guy, cable, line, halser^†, hawser, painter, moorings, wire, chain; string etc. (filament) 205.    fastener, fastening, tie; ligament, ligature; strap; tackle, rigging; standing rigging, running rigging; traces, harness; yoke; band ribband, bandage; brace, roller, fillet; inkle^†; with, withe, withy; thong, braid; girder, tiebeam; girth, girdle, cestus^†, garter, halter, noose, lasso, surcingle, knot, running knot; cabestro [U.S.], cinch [U.S.], lariat, legadero^†, oxreim^†; suspenders.    pin, corking pin, nail, brad, tack, skewer, staple, corrugated fastener; clamp, U-clamp, C-clamp; cramp, cramp iron; ratchet, detent, larigo^†, pawl; terret^†, treenail, screw, button, buckle; clasp, hasp, hinge, hank, catch, latch, bolt, latchet^†, tag; tooth; hook, hook and eye; lock, holdfast^†, padlock, rivet; anchor, grappling iron, trennel^†, stake, post.    cement, glue, gum, paste, size, wafer, solder, lute, putty, birdlime, mortar, stucco, plaster, grout; viscum^†.    shackle, rein etc. (means of restraint) 752; prop etc. (support) 215.    ... show more

Roget 752: prison, prison house; jail, gaol, cage, coop, den, cell; stronghold, fortress, keep, donjon, dungeon, Bastille, oubliette, bridewell^†, house of correction, hulks, tollbooth, panopticon^†, penitentiary, guardroom, lockup, hold; round house, watch house, station house, sponging house; station; house of detention, black hole, pen, fold, pound; inclosure etc. 232; isolation (exclusion) 893; penal settlement, penal colony; bilboes, stocks, limbo, quod [Lat.]; calaboose, chauki^†, choky^†, thana^†; workhouse [U.S.].    Newgate, Fleet, Marshalsea; King's Bench, Queen's Bench.    bond; bandage; irons, pinion, gyve, fetter, shackle, trammel, manacle, handcuff, straight jacket, strait jacket, strait-jacket, strait-waistcoat, hopples^†; vice, vise.    yoke, collar, halter, harness; muzzle, gag, bit, brake, curb, snaffle, bridle; rein, reins; bearing rein; martingale; leading string; tether, picket, band, guy, chain; cord etc. (fastening) 45; cavesson^†, hackamore [U.S.], headstall, jaquima [U.S.], lines, ribbons.    bolt, deadbolt, bar, lock, police lock, combination lock, padlock, rail, wall, stone wall; paling, palisade; fence, picket fence, barbed wire fence, Cyclone fence, stockade fence, chain-link fence; barrier, barricade.    drag etc. (hindrance) 706.    ... show more

Dutch: breidel, lei, leidsel, leiriem, teugel, tuigage
Polish: wodze, cugle, wodza, lejce

Any means of control.

Control and direct with or as if by reins:
— Rein a horse.

synonyms: draw rein, harness, rein in.

Stop or slow up one's horse or oneself by or as if by pulling the reins:
— They reined in in front of the post office.

synonym: rein in.

Dutch: beteugelen

Stop or check by or as if by a pull at the reins:
— He reined in his horses in front of the post office.

synonym: rein in.

Keep in check.

synonyms: harness, rule.