To deceive means to trick or lie. A crafty kid might deceive his mother into thinking he has a fever by holding the thermometer to a light bulb to increase the temperature.
Deceive is the trickier cousin of lie. You might lie about why you were late to school. But if you simply don't explain to your mom that you were late in the first place, you are deceiving her. Deceive carries with it a feeling of both craftiness and betrayal. When you deceive someone, forgiveness can be hard to come by. Have you heard of the spelling rule, "i before e except after c" that has so many exceptions? Well, deceive follows that rule.