grow a tail

verb3

1. •
   (slang, vulgar) To defecate; to have a bowel movement.

   • When man needs to grow a tail, man must run to bathroom without fail. Thou shalt groweth thy tail with great care, or though might staineth thine underwear! — 2000
2. •
   (slang, vulgar) To struggle to hold back an imminent bowel movement.
3. •
   (slang, vulgar) To have a protuberance (a bump) be formed on the rear of one's bottomwear (viz. pants, underpants, diaper, etc.) after a particularly productive incident of solid fecal incontinence.