tread

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

• intransitive verb To walk on, over, or along.
• intransitive verb To press beneath the feet; trample.
• intransitive verb To treat unjustly or harshly; oppress.
• intransitive verb To form by walking or trampling.
• intransitive verb To execute by walking or dancing.
• intransitive verb To copulate with. Used of a male bird.
• intransitive verb To go on foot; walk.
• intransitive verb To set down the foot; step.
• intransitive verb To trample something. Used with on or upon.
• intransitive verb To treat someone or something unjustly or harshly. Used with on or upon.
• intransitive verb To copulate. Used of birds.
• noun The act, manner, or sound of treading.
• noun An instance of treading; a step.
• noun A mark made by treading, as in snow.
• noun The upper horizontal part of a step in a staircase.
• noun The part of a wheel or tire that makes contact with the road or rails.
• noun The grooved face of a tire.
• noun The part of a shoe sole that touches the ground.
• noun Either of the continuous ridged belts with which bulldozers, tanks, and certain other vehicles move over the ground.
• idiom (tread the boards) To act on the stage.
• idiom (tread water) To keep the head above water while in an upright position by pumping the legs.
• idiom (tread water) To expend effort but make little or no progress to achievement of a goal or an end.

from The Century Dictionary.

• noun Any horizontal element in a floor upon which the walker treads or presses, and so gives an alarm or makes a signal.
• To form puddles under the tread of horses: said of the ground.
• To set the foot down, as on the ground.
• To press or be put down on or as on the ground.
• To walk; step; especially, to walk with a more or less stately, measured, or cautious step.
• To copulate, as birds: said especially of a cock-bird.
• To follow closely.
• To step or walk on.
• To beat or press with the feet: as, a well-trodden path.
• To crush under the foot; trample in contempt or hatred.
• To dance.
• To walk.
• To copulate with or cover, as a bird.
• To destroy, extinguish, or obliterate by or as by treading or trampling.
• noun A step or stepping; footing; pressure with the foot.
• noun Way; track; path. See trade, n. 2.
• noun Copulation, as of birds.
• noun The cicatricula of an egg: so called from the former erroneous belief that it appeared only in fecundated eggs laid by the hen after the tread of the cock. Compare treadle.
• noun Manner of stepping: as, a horse with a good tread.
• noun The flat or horizontal part of a step or stair; a tread-board.
• noun The length of a ship's keel.
• noun The bearing surface of a wheel or of a runner on a road or rail.
• noun The part of a rail on which the wheels bear.
• noun The part of a stilt on which the foot rests.