The depth to which a chess program analyzes the possible, likely, and ideal moves of a chess game. 1 ply means all currently legal moves and their value, and 2 ply handles the possibilities that arise from those possibilities similarly. The 30th ply takes much longer to compute than the 1st ply. Algorithms and clever code enable shortcuts and even better chances that the computer will kick your ass.
by Shnermeltzerwitz November 24, 2013