1. Lacking proof or substantiation

See also: unproved, unproven

• undeviating
• undiagnosable
• undiagnosed
• undies
• undifferentiated
• undigested
• undignified
• undiluted
• undiminished
• undimmed
• undine
• undiplomatic
• undiplomatically
• undirected
• undiscerning
• undischarged
• undiscipline
• undisciplined
• undisclosed
• undiscouraged
• undiscoverable
• undiscovered
• undiscriminating
• undisguised
• undismayed