Well, what would you call it? Have a look at the images below (source):
If you would call what other species have tails, then the human one should also be called so. After all, they are extremely similar (the last image, k, is human):
a Echidna or spiny anteater (Tachyglossus aculeatus).
Because of the extreme rarity of monotreme material we
were only able to obtain this embryo, which is younger than the
tailbud stage. b Brush-tailed possum (Trichosurus vulpecula). c
Eastern Australian native “cat” (Dasyurus quoll). d Domestic cat*
(Felis catus). e Domestic dog (Canis familiaris). f Domestic sheep
(Ovis aries). g Scaly anteater (Manis javanica). h Rat (Rattus norvegicus).
i Rabbit (Oryctolagus cuniculus). j Hedgehog (Erinaceus
europaeus). k Human (Homo sapiens).
The above image was taken from M.K. RIchardson et. al.,Anat Embryol (1997) 196:91–106 (a PDF can be found here)