ETYM Shortened from aback.
1. At or to or toward or the back or rear; SYN. backward, backwards, rearward, rearwards.
2. In answer; SYN. in reply.
3. In or to or toward a former location.
4. In or to or toward a past time; SYN. backward.
5. In or to or toward an original condition.
6. In repayment or retaliation.
1. In or into an inferior position.
2. In or to or toward the rear.
3. Remaining in a place or condition that has been left or departed from.
4. Of timepieces; SYN. slow.
5. In debt; SYN. behindhand, in arrears.