adjectives
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
is similar to
showing lack of care for consequences
"behaved like an irresponsible idiot"; "hasty and irresponsible action"