guileful, conniving, deceitful, irresponsible, unreliable, untrustworthy, dangerous, desultory, doubtful, dubious, fly-by-night, hazardous, insecure, perilous, precarious, questionable, risky, rocky, shaky, shifting, shifty, slippery, ticklish, treacherous, uncertain, undependable, unhealthy, unpredictable, unsafe, unsound, unstable, unsteady, unsubstantial, unsure