Words That Rhyme With "Flattening" :
3 syllables:
antonym, battening, brightening, captaining, fattening, frightening, happening, heightening, maddening, patenting, saddening, santonin, saponin, straightening, sweetening, tightening
antonym, battening, brightening, captaining, fattening, frightening, happening, heightening, maddening, patenting, saddening, santonin, saponin, straightening, sweetening, tightening