1.Definition: (used especially of persons) not dependable in devotion or affection; unfaithful

"When lovers prove untrue"

Related Adjective(s):false

2.Definition: not according with the facts

"Unfortunately the statement was simply untrue"

3.Definition: not accurately fitted; not level

"Off-level floors and untrue doors and windows"

4.Definition: not true to an obligation or trust

"Is untrue to his highest opportunity and duty"