Main entry: thwart, cross thwart
Definition: a crosspiece spreading the gunnels of a boat; used as a seat in a rowboat
Main entry: spoil, scotch, queer, thwart, bilk, baffle, foil, frustrate, cross
Definition: hinder or prevent (the efforts, plans, or desires) of
Usage: What ultimately frustrated every challenger was Ruth's amazing September surge; foil your opponent