(someone is) buckled up

A "buckle" is the part of a belt where you attach the two ends to each other. The belts people wear on their pants have buckles. So do some shoes, straps for handbags and luggage, and seatbelts.

The buckle on a seatbelt gives us the phrase "buckled up", which means having your seatbelt closed and attached.

This phrase appears in these lessons: