Here's what rhymes with undersew.
so though show tho fo foe ho ceux faut hoe sew soe vo sho zo no know go low ago co flow slow snow throw row lo undergo bo doe dough fro mo po ro toe wo woe thro tow yo beau goe jo ko uno beaux cho dau floe mow noe roe yeux dunno rho stow throe sloe tarot turbot undertow whoa doh borzoi schmo schmoe although below blow grow pro glow plateau quo bestow chateau crow hello indigo bio nouveau propos tableau aglow dicho tableaux topos tuo bro chateaux plateaux trousseau trow chapeau kapok deathblow kayo matzoh pompano chapeaux pekoe trousseaux resew ratio embryo overthrow audio buffalo overflow folio patio bungalow dynamo forego forgo polio aliquot apropos domino escrow medico outgrow siglo afterglow adagio oleo piccolo foreknow bandeau gateau fatso gateaux tallyho radio studio portico stereo calico vertigo cameo mistletoe rodeo spatio pistachio overgrow regrow mustachio romeo moustachio politico presidio oregano microdot portfolio archipelago impresario braggadocio pianissimo generalissimo