dealer vs pusher

dealer and pusher both are nouns.

Word	Noun	Adjective	Verb	Adverb
dealer	Yes	No	No	No
pusher	Yes	No	No	No

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

Other hyponyms of dealer include drug dealer, drug peddler, drug trafficker, peddler.

dealer (noun)	pusher (noun)
a firm engaged in trading	a small vehicle with four wheels in which a baby or child is pushed around
a seller of illicit goods	a sandal attached to the foot by a thong over the toes
the person who distributes the playing cards in a card game	someone who pushes
someone who purchases and maintains an inventory of goods to be sold	an unlicensed dealer in illegal drugs
the major party to a financial transaction at a stock exchange; buys and sells for his own account	one who intrudes or pushes himself forward