See thwart in Webster's New World Roget's A-Z Thesaurus II
verb
To prevent from accomplishing a purpose:
baffle, balk, check, checkmate, defeat, foil, frustrate, stymie. (Informal) cross, stump. Idiom: cut the ground from under. See allow
adjective
Situated or lying across:
crossing, crosswise, transversal, transverse, traverse. See horizontal
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