Wiktionary
n. A type of trading card that features a picture of a baseball player on one side and information about the player on the other side.
WordNet
n. a trading card with a picture of a baseball player and information about his playing record
Wikipedia
A baseball card is a type of trading card relating to baseball, usually printed on some type of paper stock or card stock. A card will usually feature one or more baseball players or other baseball-related sports figures. Cards are most often found in the US but are also common in countries such as Canada, Cuba, and Japan, where top-level leagues are present with a substantial fan base to support them. Some companies that are notable for making these cards include Topps, Upper Deck, and Panini. Previous manufacturers include Fleer (now a brand name owned by Upper Deck), Bowman (now a brand name owned by Topps), and Donruss (now a brand name owned by Panini Group). Baseball cards can be highly collectible and valuable.
Usage examples of "baseball card".
There was a cow's skull half-buried in the ground where the discarded batteries had been and an old rusty horseshoe where the potato-chip bag had been, but the wrapper from the baseball cards was still there.