adhesional

Century Dictionary and Cyclopedia

1. Of the nature of or depending upon adhesion; applied specifically to the action of locomotives when the smooth driving-wheel, running on a plane rail, is prevented, through the weight of the engine, from slipping on the rail by its adhesion thereto. When the power of the cylinder applied to turn the wheel exceeds this effect of adhesion, and friction of motion ensues by the slipping of the wheel on the rail, the tractive power becomes less. When the grades become too steep for adhesional traction because the cylinder-diameter necessary to overcome the resistance will cause the wheels to slip, the tractive effort must be exerted through toothed gears meshing into a rack or toothed rail, while the weight may be still carried on smooth rails by ordinary wheels.

Wiktionary

1. adj. Relating to adhesion.