Open English Wordnet
Nouns
(n)thwart, cross thwarta crosspiece spreading the gunnels of a boat; used as a seat in a rowboat Verbs
(v)thwart, queer, spoil, scotch, foil, cross, frustrate, baffle, bilkhinder or prevent (the efforts, plans, or desires) of“What ultimately frustrated every challenger was Ruth's amazing September surge”,
“foil your opponent”