Sexual desire.
From Wikipedia on 22-May-2013
URL: http://en.wikipedia.org/wiki/Lust
Lust is an intense desire or craving. Lust can take many forms such as the lust for knowledge, the lust for sex or the lust for power. It can take such mundane forms as the lust for food as distinct from the need for food. Lust is a powerful psychological feeling producing intense wanting for an object, or circumstance fulfilling a it. Many religions separate the definition of passion and lust by further categorizing lust as type of passion for something that does not belong to oneself