The Oxford Thesaurus An A-Z Dictionary of Synonyms - infirmadj.

1) ill, indisposed, debilitated, frail, fragile, weak, feeble, weakened, ailing, decrepit, enfeebled, failing, wasted, on the decline, sick, sickly, unwell, lame, crippled: Campbell is infirm and unable to travel. 2) shaky, flimsy, wobbly, wobbling, doddering, unstable, faltering, vacillating, wavering, unsteady, unsteadfast, inconstant, changeable, irresolute: We must find stalwart recruits, recruits who are not infirm of purpose.