placard vs show bill

placard and show bill both are nouns.

Word	Noun	Adjective	Verb	Adverb
placard	Yes	No	Yes	No
show bill	Yes	No	No	No

As nouns, show bill is a hyponym of placard; that is, show bill is a word with a more specific, narrower meaning than placard:

Other hyponyms of placard include show card, theatrical poster, flash card, flashcard.

placard (noun)	show bill (noun)
a sign posted in a public place as an advertisement	a poster advertising a show or play

placard (verb)	show bill (verb)
publicize or announce by placards
post in a public place