safety bicycle

from the GNU version of the Collaborative International Dictionary of English.

• A bicycle with equal or nearly equal wheels, usually about 28 inches diameter, driven by pedals connected to the rear (driving) wheel by a multiplying gear. Since the 1930's this has been the most common type of bicycle, now simply called bicycle. The older high-wheelers are often referred to as bone-rattlers.

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

• noun bicycle that has two wheels of equal size; pedals are connected to the rear wheel by a multiplying gear