General: train position
A sex position involving at least 3 individuals, but can include an unlimited number of participants.
The train position refers to a specific position where the participants form a line, front to back, and penetrate whoever is in front of them (anally or vaginally) much like the linked boxcars on a train. However, the last one being penetrated can be penetrated vaginally, anally, or orally.
For an oral-only trainlike position, please use daisy chain.