副词

介词

了解海关手续

1. 在（船、飞机等）上
If you are aboard a ship or plane, you are on it or in it.

1. on first or second or third base

e.g. Their second homer with Bob Allison aboard

Synonym: on base

2. on a ship, train, plane or other vehicle

Synonym: on board

3. part of a group

e.g. Bill's been aboard for three years now

4. side by side

e.g. anchored close aboard another ship

Synonym: alongside