dealer vs horse trader

dealer and horse trader both are nouns.

Word	Noun	Adjective	Verb	Adverb
dealer	Yes	No	No	No
horse trader	Yes	No	No	No

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

dealer: someone who purchases and maintains an inventory of goods to be sold
horse trader: a hard bargainer

dealer (noun)	horse trader (noun)
a firm engaged in trading	a hard bargainer
a seller of illicit goods
the person who distributes the playing cards in a card game
someone who purchases and maintains an inventory of goods to be sold
the major party to a financial transaction at a stock exchange; buys and sells for his own account