Fleetingly rhymes with:
devastatingly, disappointingly, excruciatingly, fittingly, frustratingly, haltingly, hauntingly, interestingly, lastingly, mattingly, pointingly, regulatingly, sportingly, unhesitatingly, unwittingly, wittingly
devastatingly, disappointingly, excruciatingly, fittingly, frustratingly, haltingly, hauntingly, interestingly, lastingly, mattingly, pointingly, regulatingly, sportingly, unhesitatingly, unwittingly, wittingly