adj. 25B6; adjective
the building was unsafe : DANGEROUS, risky, perilous, hazardous, life-threatening, high-risk, treacherous, insecure, unsound; harmful, injurious, toxic.
the verdict was unsafe : UNRELIABLE, insecure, unsound, questionable, open to question/doubt, doubtful, dubious, suspect, fallible; informal iffy.
harmless, secure.