a.

1. 体弱的；（因年迈而）衰弱的
   Great-grandmother was old and infirm.

   曾祖母年迈体弱。

2. 意志薄弱的；不坚定的；优柔寡断的
   Hunter is infirm of purpose.

   亨特为人优柔寡断。

3. （构造物）不稳固的，动摇的
4. 不牢靠的；不生效的
   an infirm title to property

   不牢靠的产权

adj.

1. not physically strong, especially through age.
2. archaic irresolute; weak.