car·pool 
(kärpl′)
(kärpl′)n. also car pool
1. An arrangement whereby several participants or their children travel together in one vehicle, the participants sharing the costs and often taking turns as the driver.
2. A group, as of commuters or parents, participating in a carpool.
v. also car-pool car·pooled, car·pool·ing, car·pools
v.intr.
To travel in a carpool.
v.tr.
To transport by means of a carpool: carpool the children to school.
carpool′er n.