a firm engaged in trading
"The investment bank acted as a dealer, buying and selling government bonds for its clients on a continuous basis."
the person who distributes the playing cards in a card game
"As soon as the dealer shuffled the deck, everyone leaned forward to watch the deal."
One who deals in goods, especially automobiles; a middleman.
"After weeks of searching, they finally found a reputable car dealer who offered them a fair price for their used sedan."
In plain English: A dealer is someone who sells goods or services for a living.
"The car dealer explained the warranty terms to the new customer."
Usage: A dealer is a person or business that buys and sells specific types of goods, such as cars, securities, or drugs, acting as an intermediary between manufacturers and consumers. Use this term to describe anyone engaged in the commercial exchange of particular items rather than just retailing general merchandise.
The word dealer comes from the Old English dǣlere and originally meant a distributor or apportioner of goods. Its modern sense evolved naturally as it became associated with someone who deals in cards or other commodities.