What is Definition of over and back?

In Basketball, once an offensive player passes the half court line with both feet and the ball, the team may not take the ball into the back court unless it is deflected (last touched) by the defense. A player who has just crossed the line with the ball and brings it back into the backcourt is not "over & back". They have not yet established the ball in the front court, therefore cannot have a backcourt violation