not reliable; not to be relied or depended on.

adjective

honest , reliable , responsible , true , trustworthy

adjective

capricious , deceitful , deceptive , delusive , disreputable , dubious , erroneous , fake , fallible , false , fickle , fly-by-night * , furtive , hallucinatory , hollow , implausible , inaccurate , inconstant , irresponsible , makeshift , meretricious , mistaken , pretended , pseudo * , questionable , sham , shifty , specious , treacherous , tricky , uncertain , unconvincing , undependable , underhand , underhanded , unfaithful , unsound , unstable , unsure , untrue , untrustworthy , vacillating , wavering , weak , arbitrary , changeable , dangerous , duplicitous , erratic , feckless , fitful , flighty , fly-by-night , haphazard , impetuous , impulsive , mercurial , quicksilver , random , shifting , shiftless , skittish , tenuous , unconscionable , unpredictable , unprincipled , unsafe , unscrupulous , untenable , villainous , volatile , whimsical