A two-handed card duel of melding and trick-taking, played with a 48-card double deck where the same cards count twice.
Cards rank A, 10, K, Q, J, 9 from high to low. The game runs in two phases. While the stock lasts you need not follow suit; win a trick, draw the top card, and you may then declare a meld. Once the stock is gone you must follow suit and win the trick if you can.
Pinochle traces back to bezique by one of two routes, and the sources do not settle between them: either it is a cousin of the German Binokel with both descending from bezique, or it grew out of Binokel directly.
The name is the interesting part. The likeliest derivation is the French binocle — "two eyes", or eyeglasses — from the notion that the German game used a special deck on which the queen of spades and the jack of diamonds were drawn in side profile, showing one eye each. Those two cards are still the meld the game is named for.
A rival explanation derives it from bis and Knöchel, "knuckle", on the grounds that a game originally ended when a player rapped the table. Neither account is settled, which is ordinary for card-game etymology and worth saying rather than choosing the tidier one.
Pinochle is a traditional public-domain melding card game. This is an original, free browser version of the two-handed game with a CPU opponent and online head-to-head play.