(n)hydrofoil, foila device consisting of a flat or curved piece (as a metal plate) so that its surface reacts to the water it is passing through“the fins of a fish act as hydrofoils”
(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”