The Collaborative International Dictionary of English v.0.48:

Ruble \Ru"ble\, n. [Russ. ruble.]
   The unit of monetary value in Russia.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ruble
    n 1: the basic unit of money in Tajikistan
    2: the basic unit of money in Russia [syn: ruble, rouble]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "ruble":
   Deutschmark, Mark, Reichsmark, afghani, anna, baht, cent, centavo,
   centime, conto, dollar, dong, florin, franc, guilder, gulden, kip,
   kopeck, krona, krone, lira, milreis, peseta, pie, piece of eight,
   pistareen, pound, rand, rial, rupee, shekel, shilling, sol, sou,
   stiver, won, yen