Definition of thwarts:
(v) :
(transitive) To cause to fail; to frustrate, to prevent.
(adj) :
Placed or situated across something else; cross, oblique, transverse.
(adj) :
(figuratively, dated) Of people: having a tendency to oppose; obstinate, perverse, stubborn.
(adj) :
(figuratively, dated) Of situations or things: adverse, unfavourable, unlucky.
(n) :
(nautical) A seat across a boat on which a rower may sit.
(n) :
(nautical) A brace, perpendicular to the keel, that helps maintain the beam (“breadth”) of a marine vessel against external water pressure and that may serve to support the rail.