The Oxford Thesaurus An A-Z Dictionary of Synonyms - infirmity n.

1) weakness, feebleness, frailness, frailty, debility, decrepitude, sickliness: At 100, she finally succumbed to infirmity, and ceased going out altogether. 2) sickness, ailment, disease, malady, affliction, disorder, defect, complaint: What infirmity struck him down?