1. Tested and proved to be reliable
   - tested, time-tested, tried

See also: dependable, reliable

• unproper
• unprophetic
• unpropitious
• unpropitiously
• unpropitiousness
• unprotected
• unprotectedness
• unprotective
• unprotesting
• unprotestingly
• unprovable
• unproved
• unproven
• unprovided for
• unprovocative
• unprovoked
• unprovoking
• unpublishable
• unpublished
• unpunctual
• unpunished
• unpurified
• unputdownable
• Unq
• unqualified