Paperboard rhymes with:
checkerboard, containerboard, fiberboard, fibreboard, fingerboard, linerboard, overboard, plasterboard, aboveboard, baseboard, billboard, blackboard, cardboard, checkerboard, chessboard, chipboard, clapboard, clipboard, containerboard, dartboard, dashboard, fiberboard, fibreboard, fingerboard, floorboard, hardboard, headboard, inboard, keyboard, linerboard, mopboard, onboard, outboard, overboard, pegboard, plasterboard, pressboard, scoreboard, seaboard, shipboard, skateboard, smorgasbord, snowboard, springboard, storyboard, surfboard, switchboard, wallboard, washboard
Paperboard sounds like:
parpart, perforate, perforated, pervert, perverted, prefered, preferred, prepared, probert, proffered, proofread, property, propriety, purebred, purport, purported