Pliers with a joint adjustable to two positions in order to increase the opening of the jaws WordNet 3.0 & Open English WordNet

Slip joint pliers are pliers whose pivot point or fulcrum can be moved to increase the size range of their jaws. Wikipedia

A type of plier whose pivot point or fulcrum can be moved to increase the size range of their jaws. OmegaWiki

A type of slip-joint pliers with serrated jaws generally set 45– to 60-degrees from the handle, in which the lower jaw can be moved to a number of positions by sliding along a tracking section under the upper jaw, to create different jaw spans. OmegaWiki