adj. 25B6; adjective
a frail old lady : WEAK, delicate, feeble, enfeebled, debilitated; infirm, ill, ailing, unwell, sickly, poorly, in poor health.
a frail structure : FRAGILE, breakable, easily damaged, delicate, flimsy, insubstantial, unsteady, unstable, rickety; formal frangible.
strong, robust.