infirm
/ɪnˈfɜːm/adjective
1- not physically or mentally strong, especially through age or illness（尤指因年老、疾病而）体虚的; 脆弱的。
1.1
- archaic (of a person or their judgement) weak; irresolute〈古〉（人, 判断力）软弱的; 犹豫不决的, 优柔寡断的：
he was infirm of purpose.
他意志薄弱。
派生词
infirmly
adverb词源
late Middle English （in the general sense 'weak, frail'）: from Latin infirmus, from in- 'not' + firmus 'firm'.