(adj) not worthy of reliance or trust, Syn. undependable, Ant. reliable, dependable, Example:in the early 1950s computers were large and expensive and unreliable; an undependable assistant
a. Not reliable; untrustworthy. See Reliable. -- Un`re*li"a*ble*ness, n. [1913 Webster]
Alcibiades . . . was too unsteady, and (according to Mr. Coleridge's coinage) “unreliable;” or perhaps, in more correct English, too “unrelyuponable.” De Quincey. [1913 Webster]