American Dictionary of the English Language

UNFIRM', adjective [See Firm.]

1. Not firm; weak; feeble; infirm.

[Note. When we speak of the weakness of the human frame, we use infirm. When we speak of the weakness of other things, as a bridge, wall and the like, we say, it is unfirm ]

2. Not stable; not well fixed.

With feet unfirm