And even though computer programs TRY to make it hard for people to commit such acts of accidental suicide, they still happen. It means to remove completely and forever. It means to remove without leaving a trace. David acknowledges both the sin he has committed and his need for cleansing. He is also abundantly aware that he is in his very nature sinful.
All human beings have a congenital tendency toward evil.
At least, that's what we read in our versions. He asks God to take the sin right out of him, to remove it without a trace as if it had never been. As well as asking God to take something out, however, David also asks God to put something in. Old destructive ways of thinking and acting must be replaced by new positive ones. Fear must be replaced by faith.