1. Extremely alarming
   - hair-raising, nightmarish

See also: alarming

• undiscipline
• undisciplined
• undisclosed
• undiscouraged
• undiscoverable
• undiscovered
• undiscriminating
• undisguised
• undismayed
• undisputable
• undisputed
• undisputedly
• undissolved
• undistinguishable
• undistinguished
• undistorted
• undistributed
• undisturbed
• undiversified
• undividable
• undivided
• undivided interest
• undivided right
• undo
• undoable