1.the fleshy part of the human body that you sit on;
he deserves a good kick in the butt
2.having the lower score or lagging position in a contest;
behind by two points
3.in or to or toward the rear;
he followed behind
4.remaining in a place or condition that has been left or departed from;
when he died he left much unfinished work behind
5.of timepieces;
the clock is almost an hour slow
6.in or into an inferior position;
fell behind in his studies
7.in debt;
he fell behind with his mortgage payments