Semi-sentient stone creatures which are used as guards for rooms in Hogwarts. A stone gargoyle blocks the entrance to the Head’s Office. It steps aside when the correct password is given to enter (CS11). Two stone gargoyles guard the staff room and sarcastically challenge students who attempt to get into the room (OP17). A stone gargoyle is used as a water spout in the Potions dungeon (PA17).
The term is also used as an interjection ("Gulpin' Gargoyles!") and as a disparaging nickname for someone who is mean and unbending (e.g. "Yeh don' know them gargoyles at the Committee fer the Disposal o' Dangerous Creatures!"), rather stupid ("And if you'll believe me, lads, the gormless gargoyle buys all 'is own toads back orf me for a lot more'n what 'e paid in the first place -"), or even completely despicable ("That foul, lying, twisting old gargoyle!", which Hemione said of Umbridge).