let down vs thwart

let down is not a noun while thwart is a noun.

Word	Noun	Adjective	Verb	Adverb
let down	No	No	Yes	No
thwart	Yes	No	Yes	No

As verbs, thwart is a hypernym of let down; that is, thwart is a word with a broader meaning than let down:

Other hypernyms of let down include baffle, bilk, cross, foil, frustrate, queer, scotch, spoil.

let down (noun)	thwart (noun)
	a crosspiece spreading the gunnels of a boat; used as a seat in a rowboat

let down (verb)	thwart (verb)
fail to meet the hopes or expectations of	hinder or prevent (the efforts, plans, or desires) of
move something or somebody to a lower position