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A long furry (or scaly) appendage protruding from the lower back. A common feature of cat girls.
In general, don't tag this on an animal unless there's something special or noteworthy about the tail, such as one of the many tags below that implicate this tag like heart tail or tail hold, or if the image is focused on the tail. Definitely don't tag an animal with a tail of its own type, like tagging cat tail on a cat. (Do tag weird combos like a bunny tail on a cat, though.)
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The following tags are aliased to this tag: tails, shippo, animal_tail, and animal_tails (learn more).
The following tags implicate this tag: cat_tail, fox_tail, bunny_tail, tail_grab, demon_tail, tail_hug, tail_through_clothes, dragon_tail, wolf_tail, cow_tail, mouse_tail, tail_between_legs, heart_tail, tail_biting, tail_bell, tail_ribbon, dog_tail, raccoon_tail, tiger_tail, lion_tail, bear_tail, multiple_tails, squirrel_tail, tail_masturbation, tail_wrap, tail_fondling, tail_rape, tail_ornament, tail_hold, pikachu_tail, horse_tail, salamander_tail, forked_tail, tail_bow, pig_tail, reindeer_tail, laevatein_(tail), tapir_tail, monkey_tail, multicolored_tail, serval_tail, spiked_tail, alpaca_tail, mechanical_tail, striped_tail, holding_tail, weasel_tail, beaver_tail, fake_tail, lizard_tail, long_tail, holding_another's_tail, leopard_tail, sheep_tail, holding_own_tail, penguin_tail, chameleon_tail, fiery_tail, jaguar_tail, prehensile_tail, prairie_dog_tail, moose_tail, scorpion_tail, otter_tail, snake_tail, dinosaur_tail, rat_tail, fish_tail, and large_tail (learn more).