uncrossed - ussingite
- unresolved echo
- unrestricted
- unripe
- unrivalled opportunity
- unroofed
- unroofing
- unsaturated
- unscreened
- unscreened coal
- unsealed
- unsealed place
- unsegmented
- unseptate
- unsettled weather
- unshrinkable
- unsize
- unsized
- unsized coal
- unspawned
- unsprung
- unstable
- unstable floor
- unstable ground
- unstable nucleus
- unstable rock
- unstable roof
- unstable type
- unstacked seismic data
- unsteady
- unsteady flow
- unstrained
- unstratified
- unstratified deposit
- unstratified drift
- unstratified rock
- unstressed half-space
- unstressed medium
- unstuck
- unsuccessful well
- unsupported