impecunious vs hard up

impecunious and hard up both are adjectives.

Word	Noun	Adjective	Verb	Adverb
impecunious	No	Yes	No	No
hard up	No	Yes	No	No

As adjectives, impecunious and hard up are synonyms defined as:

Other synonyms of impecunious include in straitened circumstances, penniless, penurious, pinched.

impecunious (adjective)	hard up (adjective)
not having enough money to pay for necessities	not having enough money to pay for necessities