Synonyms for Thwart:

n.

aft, amidships, bay, beam, berth, bilge, blade, boom, bow, bowsprit. allow, checkmate, defeat, disturb, silence, stump, stymie, keep from, cut the ground from under. thwart (noun)
baffle, bilk, cross, cross thwart, foil, frustrate, scotch, spoil.

v.

disappoint (verb)
dash, disappoint, disconcert, discourage, dishearten, disillusion.
hinder (verb)
baffle, bar, block, bottleneck, brake, bung, burden, catch, check, choke, clog, complicate, congest, constipate, constrain, counter, cramp, crimp, cripple, curb, dam, delay, detain, deter, drag, encumber, entangle, entrap, fetter, foul, frustrate, hamper, hamstring, handicap, hinder, impair, impede, inhibit, interrupt, jam, mire, obstruct, oppose, paralyze, plug, resist, restrain, restrict, snag, snarl, stay, stop, tangle.
stop (verb)
confuse, trammel, study at frustrate.
stop, hinder (verb)
baffle, bilk, check, confuse, counter, cramp, crimp, cross, curb, dash, defeat, disappoint, foil, frustrate, impede, obstruct, oppose, restrain, scotch, stymie, trammel.

Other synonyms:

stymie. silence, stump. defeat, disturb. countermove
checkmate.
halt
checkmate.
hinder
baffle.
impede
trammel.
resist
keep from.
trammel
trammel.
Other relevant words:
bilk, checkmate, confuse, cross, cross thwart, defeat, disturb, foil, scotch, spoil, stump, stymie, trammel, keep from, cut the ground from under.

Usage examples for thwart

  1. She and her husband plot, and I plot to thwart them. – Vittoria, v8 by George Meredith
  2. No more am I; give me everything I want, and never thwart me, and I am the easiest fellow to live with in the world. – Dr. Jolliffe's Boys by Lewis Hough
  3. I tried hard, with the aid of 150 burghers, to thwart his plans and we had some fighting. – My Reminiscences of the Anglo-Boer War by Ben Viljoen