alarming, bad, chancy, critical, dangerous, dangersome, delicate, desultory, explosive, fraught with danger, hairy, hazardous, infirm, insecure, insubstantial, jeopardous, menacing, parlous, periculous, precarious, provisional, risky, serious, shaky, shifting, shifty, slippery, susceptible, temporary, tentative, threatening, ticklish, tottery, touchy, treacherous, ugly, uncertain, undependable, unfaithworthy, unhealthy, unreliable, unsafe, unsolid, unsound, unstable, unsteadfast, unsteady, unsubstantial, unsure, untrustworthy, vulnerable, wicked