The tail of a horse or cow, allowed to grow out and then trimmed horizontally so as to form a tassel; a horse or cow having such a tail.
1851, Turning Out a Bagman: A Legend of Brighton Downs, in Charles Dickens, William Harrison Ainsworth, Albert Smith Bentley's Miscellany, Volume XXIX, page 259,
Two lean, ewe-necked, clipt chestnuts, tucked up in the ribs, with hard work and bad feeding, but with such flowing bang-tails as at once stamped them in the eyes of our friends as “ out-and-out ” thorough-breds—were led up and down by John. […] The bang-tails, no doubt, supposing themselves out for their usual “airing,” put themselves in the regular side-long position, and struck at once into a sort of hectic canter ; a particular movement, peculiar to Brighton bang-tails, and adapted to the most innocent equestrian.
1903, Tom Collins (Joseph Furphy), Such Is Life: Being Certain Extracts from the Diary of Tom Collins, 2004, page 68,
"And did you see a dark chestnut horse; bang tail; star and snip; white hind feet; saddle and bridle on?" I asked.
(US) A racehorse.
(slang) A prostitute.
(marketing) An envelope with a perforated flap on which promotional material is printed; the flap on such an envelope.
verb
To shear off the hair horizontally at the end of a cow or horse's tail.