sweep·er I. \-pə(r)\noun (-s) Etymology: Middle English swepare, from swepen to sweep + -are, -ere -er 1.: a device that cleans by sweeping < lawn sweeper > 2.: one that sweeps; specifically: one whose work is cleaning an object or area by sweeping 3.: mine sweeper II. noun orsweeper back : a lone back in soccer who plays between the line of the defenders and the goal