Basket Trade

"Basket" = grouped together. "Trade" = exchanging securities. So a basket trade is trading a group of multiple (usually 15 or more) securities at the same time.

Institutions or investment funds which are looking to purchase or sell a variety of securities in certain amounts will conduct such trades, keeping in mind the balance of their desired portfolio allocation. As the killer from Silence of the Lambs would say, "She puts the securities in the basket."