What is "colony counter"

Colony counter \Col"o*ny count`er\ (k[o^]l"[-o]*n[y^] kount"[~e]r), n. (Microbiology) an instrument designed to conveniently count or assist counting colonies[9] of microorganisms on a plate containing a gelled growth medium. One variety uses a pencil-like rod with a metal tip, which is connected by an electrical connection to the gelled growth medium; when touched to a colony[9] on the plate, the completion of the electrical circuit causes an increment of 1 unit on the readout of the colony counter.

n. (context microbiology English) laboratory equipment used to count colonies of bacteria, or other microorganisms, growing on agar, usually in a Petri dish.