what is lust?

i think lust is more of a crush, obsession kind of thing. like before you love someone, you lust them, you want to be with them. you have a crush on them. i think lust can develop into love, or can become ugly, full of spineless jealousy, slaps in the face, spying on your partner, and an unhealthy relationship. but to be honest, i just dont know the exact definition of the word. oh well =)