A small creature bred by the Klingons to devour tribbles, used to fight a tribble infestation.
The glommer was a squat creature created by Klingon scientists for one job: eating tribbles, which Klingons despise. It found and consumed tribbles quickly.
In More Tribbles, More Troubles, Koloth brought a glommer while chasing Cyrano Jones, who had bred tribbles that did not multiply but grew huge instead. The glommer could not handle the giant tribbles and fled from one. The giant tribbles themselves turned out to be colonies of smaller tribbles.