hard difficult arduous tough demanding exacting laborious strenuous challenging gruelling(UK) formidable heavy grueling(US) toilsome testing uphill rigorous rough backbreaking severe turbulent agitated choppy seething bumpy foaming boiling roily ruffled tremulous unsettled unstable weltering storm-tossed violent tempestuous raging blustery stormy toiling labouring(UK) laboring(US) striving drudging struggling slaving working sweating slogging travailing endeavouring(UK) endeavoring(US) straining hustling plodding grinding ploughing(UK) plowing(US) grubbing roiling churning swirling bubbling convulsing surging whirling rising and falling simmering frothing tossing heaving shaking jolting fizzing effervescing fermenting More