Love trains are a type of sexual act that occur during group sex where all but one individual consecutively penetrates the person in front of them.
Love trains require the participation of at least three individuals, though more is ideal. The participant in the rear must penetrate the person before them, the one in the front must be getting penetrated, and both must apply for all participants situated in the middle. This is not to be confused with double-penetration, where one individual is penetrated by two people. However, a double-penetration can nevertheless occur either at the front of a single love train or in the middle of two colliding ones.
Penetration can be anal or vaginal and can be achieved with real cocks as well as strap-on dildos.