What is the difference between a splenic rupture and laceration?

Little Difference: A laceration is a cut with a knife or other surface that would make a cut in the spleen. Rupture implies blunt force was applied and nothing external penetrated the organ. Treatment could be the same to the spleen itself, but this depends on the severity of the injury.

None: They both really mean the same thing. Since most splenic injuries are a result of blunt trauma we refer to them as having burst or ruptured. You can get a laceration implying a cut from penetration trauma or a surgical misadventure. But for the vast majority of people the spleen gets a blunt force injury causing it to burst and get " lacerated".