n. & adv.
n. 1 a bicycle or tricycle with two or more seats one behind another. 2 a group of two persons or machines etc. with one behind or following the other. 3 a carriage driven tandem.
adv. with two or more horses harnessed one behind another (drive tandem). in tandem one behind another.
[ L, = at length (of time), used punningly ]