0 past simple and past participle of unbuckle --
1 to release the buckle (= metal fastener) of a shoe, belt, etc. so that you can remove it --
Paul, having unbuckled his seatbelt in the argument, is knocked out and dragged off by an unseen person.
During this process he had unbuckled his parachute and was never able to put it back on properly.
The herculean piper, six feet three inches in height, deliberately unbuckled his instrument and put it away carefully after detaching the bellows.
Shoulder straps will be unraveled and the waist belt will be unbuckled.
A new seatbelt interlock system prevented the car from being started if the driver and a front passenger were unbuckled.
The low-cost presumption clearly will not be correct for all persons; some adults, perhaps those who experience significant discomfort, can rationally opt to ride unbuckled.