alligator clip

US /ˈæl.ɪ.ɡeɪ.tər klɪp/
UK /ˈæl.ɪ.ɡeɪ.tər klɪp/
"alligator clip" picture
1.

a clip with long, toothed jaws that is sprung shut, used for making temporary electrical connections or for holding things together

:
He used an alligator clip to connect the battery to the circuit.
The loose wires were held together with an alligator clip.