crosspiece vs thwart

crosspiece and thwart both are nouns.

Word	Noun	Adjective	Verb	Adverb
crosspiece	Yes	No	No	No
thwart	Yes	No	Yes	No

As nouns, thwart is a hyponym of crosspiece; that is, thwart is a word with a more specific, narrower meaning than crosspiece:

crosspiece: a transverse brace
thwart: a crosspiece spreading the gunnels of a boat; used as a seat in a rowboat

Other hyponyms of crosspiece include crossbar, rundle, rung, spoke, round, rung, stave, cross thwart, transom, traverse.

crosspiece (noun)	thwart (noun)
a transverse brace	a crosspiece spreading the gunnels of a boat; used as a seat in a rowboat
a horizontal beam that extends across something

crosspiece (verb)	thwart (verb)
	hinder or prevent (the efforts, plans, or desires) of