Definitions for unreliable
liable to be erroneous or misleading
"an undependable generalization"
not worthy of reliance or trust
"in the early 1950s computers were large and expensive and unreliable"; "an undependable assistant"
dangerously unstable and unpredictable
"treacherous winding roads"; "an unreliable trestle"
lacking a sense of responsibility
Kernerman English Learner's Dictionary
not able to be believed or trusted
so unreliable that you can never expect him to be here on time; unreliable evidence
not reliable; untrustworthy. See Reliable