The Collaborative International Dictionary of English v.0.48:
Unfirm \Un*firm"\, a. Infirm. [R.] --Dryden. [1913 Webster]WordNet (r) 3.0 (2006):
unfirm adj 1: not firmly or solidly positioned; "climbing carefully up the unsteady ladder"; "an unfirm stance" [syn: unfirm, unsteady] 2: (of soil) unstable; "shifting sands"; "unfirm earth" [syn: shifting, unfirm]