adv. & a. [ L. tandem at length (of time only), punningly taken as meaning, lengthwise. ] One after another; -- said especially of horses harnessed and driven one before another, instead of abreast. [ 1913 Webster ]

n. 1. A team of horses harnessed one before the other. “He drove tandems.” Thackeray. [ 1913 Webster ]

2. A tandem bicycle or other vehicle. [ Webster 1913 Suppl. ]

Tandem bicycle or
Tandem tricycle, one for two persons in which one rider sits before the other. [ 1913 Webster ]

. A kind of two-wheeled vehicle with seats back to back, the front one somewhat elevated. [ Webster 1913 Suppl. ]

. A steam engine having two or more steam cylinders in line, with a common piston rod. [ Webster 1913 Suppl. ]

. (Elec.) same as Cascade system. [ Webster 1913 Suppl. ]