hard Synonyms

difficult severe arduous tough harsh solid strong trying heavy heavily laborious stern strict unyielding challenging inflexible backbreaking firm rugged tricky taxing grueling rigorous strenuous punishing unfeeling stubborn demanding stiff toilsome resistant rigid thereabouts substantial sturdily stressful thick thickly thick-skinned thereabout testing stringent stringy swingeing strongly tangled undeniable taut surd thorny