Slowing rhymes with:
blowing, flowing, glowing, lowing, bestowing, blowing, boeing, bowing, crowing, easygoing, flowing, foregoing, forgoing, glowing, going, growing, hoeing, knowing, lowing, owing, plateauing, rowing, sewing, showing, snowing, sowing, throwing, toeing, towing, undergoing, unknowing
Slowing sounds like:
saelens, sailing, sakhalinsk, salamanca, salameh's, salamis, salem's, salinas, salinas', salinas's, saling, salling, salmans, salmons, salomon's, salonga, salons, saloons, scaling, scallions, schelling, schickling, schilling, schilling's, schillings, schlang, schlink, schooling, scowling, sealing, seeling, selena's, selinas, selinas's, selling, sellings, shallowness, shelling, shellings, shilling, shillings, sieling, silence, silences, silliness, sizzling, skilling, skillings, skolnick, skolnik, skolniks, skylines, slamming, slams, slang, slawinski, slaying, slayings, slimak, slimming, slims, sling, slings, slinky, sliwinski, sloan's, slominski, slomski, slowinski, slowness, slums, slung, slyness, solangi, soliman's, solomon's, solomos, solwin's, squealing, suckling, sullens, sullins, swallowing, swelling, swilling