The act of backtracking

To retrace one's steps.

"I dropped my sunglasses and had to backtrack to find them."

To repeat or review work already done.

"If we backtrack through this problem, maybe we can figure out where we went wrong."

To taxi down an active runway in the opposite direction to that being used for takeoff.

"Speedbird One: enter and backtrack Runway 27 Left."

To exercise a racehorse around the racetrack in the opposite direction to that in which races are run.