The Collaborative International Dictionary of English v.0.48:

Lakh \Lakh\, n.
   Same as Lac, one hundred thousand.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Lac \Lac\ (l[a^]k), Lakh \Lakh\ (l[aum]k), n. [Hind. lak,
   l[=a]kh, l[=a]ksh, Skr. laksha a mark, sign, lakh.]
   One hundred thousand; also, a vaguely great number; as, a lac
   of rupees. [Written also lack.] [East Indies]
   [1913 Webster]

WordNet (r) 3.0 (2006):

lakh
    n 1: the cardinal number that is the fifth power of ten [syn:
         hundred thousand, 100000, lakh]