ther·mo·karst 
(thûrmō-kärst′)
(thûrmō-kärst′)n.
A landscape pattern formed by the melting of permafrost and characterized by patterns of hummocks and water-filled depressions.
- UNESCO
- unessential
- uneven
- uneven bars
- unevenly
- unevenness
- uneventful
- uneventfully
- unexampled
- unexceptionable
- unexceptionably
- unexceptional
- unexceptionally
- unexpected
- unexpectedly
- unexpectedness
- unexploited
- unexpressed
- unexpressive
- unexpressively
- unexpressiveness
- unfading
- unfadingly
- unfailing
- unfailingly