形容詞 infirm:

1. lacking physical strength or vitality
   同義詞：decrepit, debile, feeble, rickety, sapless, weak, weakly
2. lacking firmness of will or character or purpose - Shakespeare

1. An infirm support.
   不堅(jiān)定的支持
2. She's old and infirm and has to keep to the house.
   她因年老體弱而足不出戶。
3. Not ailing, infirm, or diseased; healthy.
   健康的沒病的、非體弱的或沒得病的; 健康的

in.firm

adj.（形容詞）
Weak in body, especially from old age or disease; feeble.See Synonyms at weak
體弱的，衰老的：體弱的，尤指因?yàn)槟挲g大或疾??；無力的參見 weak
Lacking firmness of will, character, or purpose; irresolute.
意志不堅(jiān)的：沒有堅(jiān)強(qiáng)的意志，品質(zhì)和明確的目的；沒有決心的
Not strong or stable; shaky:
不堅(jiān)固的：不強(qiáng)大的，不牢靠的；不堅(jiān)定的：
例句：
an infirm support.
不堅(jiān)定的支持

來源：
Middle English infirme
中古英語 infirme
from Old French
源自 古法語
from Latin onfirmus
源自 拉丁語 onfirmus
in- [not] * see in-
in- [不] *參見 in-
firmus [strong, firm] * see dher-
firmus [強(qiáng)大的，堅(jiān)定的] *參見 dher-

【引伸】
infirm.ly
adv.（副詞）