uncrossed - ussingite
- underground folding
- underground gasification
- underground gravimeter
- underground hauler
- underground investigations
- underground laying
- underground leaching
- underground losses
- underground manager
- underground measurements
- underground mine
- underground mine-to-mine survey
- underground mining
- underground mining method
- underground output per man-shift
- underground pressure
- underground quarry
- underground reservoir
- underground residue
- underground shaft
- underground shovel
- underground storage
- underground structure
- underground structure contour map
- underground survey
- underground surveying
- underground transport
- underground trial
- underground waste
- underground water
- underground water parting
- underground worker
- underground working
- underground workings
- undergrowth
- underhand
- underhand stope
- underhand stoping
- underhand work
- underhang lining