A Boil
Gaṇḍa Sutta  (AN 9:15)

“Monks, it’s just as if there were a boil that had been building for many years with nine openings, nine un-lanced heads. Whatever would ooze out from it would be an uncleanliness oozing out, a stench oozing out, a disgust oozing out. Whatever would be discharged from it would be an uncleanliness discharging, a stench discharging, a disgust discharging.

“’A boil,’ monks, is another word for this body composed of the four properties, born of mother & father, fed on rice & porridge, subject to inconstancy, rubbing & massaging, breaking-up & disintegrating. It has nine openings, nine un-lanced heads. Whatever would ooze out from it would be an uncleanliness oozing out, a stench oozing out, a disgust oozing out. Whatever would be discharged from it would be an uncleanliness discharging, a stench discharging, a disgust discharging. For that reason, you should become disenchanted with this body.”

See also: MN 119; AN 4:163; Sn 1:11; Thag 10:5