skibob

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A vehicle for gliding downhill over snow, consisting of two skis one behind the other on a metal frame, steering handlebars connected to the shorter forward ski, and a low seat attached to the longer rear ski for the rider who wears small skis for balance.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A bicycle-type frame attached to skis instead of wheels, used in the sport of skibobbing.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a vehicle resembling a bicycle but having skis instead of wheels; the rider wears short skis for balancing