"thwarts" in the noun sense
1. thwart, cross thwart
a crosspiece spreading the gunnels of a boat used as a seat in a rowboat
"thwarts" in the verb sense
1. thwart, queer, spoil, scotch, foil, cross, frustrate, baffle, bilk
hinder or prevent (the efforts, plans, or desires) of
"What ultimately frustrated every challenger was Ruth's amazing September surge"
"foil your opponent"
Source: WordNet® (An amazing lexical database of English)
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