°(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