The Collaborative International Dictionary of English v.0.48:
Nylghau \Nyl"ghau\, Nylgau \Nyl"gau\, n. [Hind. & Per.
n[imac]lg[=a]w, prop., a blue cow; Per. n[imac]l blue +
g[=a]w cow. See Lilac, and Cow the animal.] (Zool.)
A large Asiatic antelope (Boselaphus tragocamelus, syn.
Portax tragocamelus), found in Northern India; called also
the blue bull. It has short horns, a black mane, and a
bunch of long hair on the throat. The general color is
grayish brown; the male is blue-grey with white markings, and
the female is brownish with no horns. [Written also
neelghau, nilgau, nylghai, and nylghaie.]
Syn: nilgai, nylghai, blue bull, Boselaphus tragocamelus.
[1913 Webster + WordNet 1.5]