legerdemain \lej-ur-duh-MAIN\, noun
1. Sleight of hand.
2. A display of skill, trickery, or artful deception.
A good magician spends countless hours practicing his legerdemain in order to make his tricks look realistic.
Legerdemain is from Old French leger de main, literally "light of hand": leger, "light" + de, "of" + main, "hand."