A bumper jack is a tall, ratcheting mechanical lift historically supplied with heavy steel-bodied cars. It features a hook that engages the lower edge of a metal bumper to raise the vehicle for tire changes. Because newer vehicles use plastic bumper covers and unibody construction, these jacks are obsolete and will crush the fascia if used on a current car.
Don't try to lift that unibody with a bumper jack or you'll rip the plastic fascia right off.
Never get under a car supported only by a bumper jack, as they are notoriously unstable and prone to slipping.
Related terms
Racing jack
A lightweight, low-profile hydraulic floor jack designed to lift a vehicle with very few pumps.
Bumper
A structure attached to the front and rear of a vehicle to absorb low-speed impacts.
Unibody
A unibody is a vehicle construction method where the floor pan and body shell are welded into a single load-bearing structure.