Synonyms and related words :
astir, at it, at work, busy, employed, en route, engaged, full of business, hard at it, hard at work, in harness, in motion, in transit, occupied, on duty, on the bum, on the gad, on the hop, on the job, on the jump, on the move, on the road, on the run, on the tramp, on the wing, tied up, under sail, under way, working