thwart
verb
°to prevent; to halt; to cause to fail; to foil; to frustrate.
"The police thwarted the would-be assassin."
noun
°(nautical) A brace, perpendicular to the keel, that helps maintain the beam (breadth) of a marine vessel against external water pressure and that may serve to support the rail.
"A well made doughout canoe rarely needs a thwart."
°(nautical) A seat across a boat on which a rower may sit.
"The fisherman sat on the aft thwart to row."
synonyms: frustrate, spoil, impede