thwart

nouns

a crosspiece spreading the gunnels of a boat; used as a seat in a rowboat
cross thwart, thwart

verbs

hinder or prevent (the efforts, plans, or desires) of
"What ultimately frustrated every challenger was Ruth's amazing September surge"; "foil your opponent"
baffle, bilk, cross, foil, frustrate, queer, scotch, spoil, thwart
is derived from
thwarter
is derived from
thwarting