unreliable
adjective
1. liable to be erroneous or misleading
Similar word(s): fallible, undependable
2. not worthy of reliance or trust
- in the early 1950s computers were large and expensive and unreliable
Similar word(s): erratic, temperamental, uncertain, unsound, untrustworthy, untrusty, undependable
3. dangerously unstable and unpredictable
- an unreliable trestle
Similar word(s): dangerous, unsafe, treacherous
4. lacking a sense of responsibility
Similar word(s): irresponsible