Lard is rendered animal fat that's used for cooking. Although many bakers use butter or vegetable shortening in their pie crust, others swear by the rich flavor of lard.
Lard is a white fat that comes from pigs. In some places, it's not uncommon to spread lard on bread instead of butter, and many cooks appreciate its ability to get extremely hot without burning and its savory flavor. Lard is also commonly used as a verb to mean "fill with unnecessary details," the way a student might lard an essay with impressive vocabulary words to disguise the fact that it was hastily written right before class.