n.

1. 兩匹馬前後縱列拉的雙輪馬車
2. 串座雙人自行車
3. 兩個以上前後排列的人（或物）

ad.

1. 一前一後地

a.

1. 一前一後的；串聯的；前後有座位的

n.

1. a bicycle with seats and pedals for two riders, one behind the other.
2. a carriage driven by two animals harnessed one in front of the other.
3. a group of two people or machines working together.

adv.