Words That Rhyme With "Slackening" :
3 syllables:
acronym, battening, beckoning, blackening, chickening, fattening, happening, maddening, patenting, quickening, reckoning, saddening, saponin, sickening, thickening, wakening, weakening
acronym, battening, beckoning, blackening, chickening, fattening, happening, maddening, patenting, quickening, reckoning, saddening, saponin, sickening, thickening, wakening, weakening