from
The Collaborative International Dictionary of English v.0.48
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.
[PJC]