- uncoil
- uncoiling
- uncolored
- unconformable bed
- unconformity
- unconformity trap
- unconsolidated
- unconsolidated formation
- uncork
- uncorrected
- uncover
- undamaged
- undecadience
- Turning point
- turnkey job
- turnover
- turnover rate
- turonian stage
- turpentine
- turps
- turrelite
- tutworkman
- twin crystal
- twin cylinder
- twin drill
- twin lamella
- twinning
- twinning plane
- twinning shear
- twisted
- twister
- two-step
- type
- type fossil
- typhonic rock
- tysonite
- ullage
- ullmannite
- ultimate production
- ultra filtration
- ultrafiltration
- umber
- un-saturation
- un-weathered
- unaffected
- unaltered
- unbedded deposit
- unbreakable
- unburned
- uncased
- uncombined carbon
- unconsolidated deposit
- undecomposed
- under-mixing
- under-stratum
- under-thrust
- under-treating
- underbed
- twin
- twin horst
- twine
- twine oil
- twinning lamella
- twinning system
- twisting
- two-stage
- two-walled
- twyer
- Tyler screen
- typical compound
- U-section
- ultimate elongation
- ultradomiant
- ultramylonite
- ultratrace
- un-converted
- un-reactive
- un-sintered
- un-worked
- unbleached paper
- uncap
- unchanged
- unconsolidated rock
- uncovered
- unctuous
- uncured
- undecene
- undecylenic
- undefined coefficient
- undependable
- under steam
- under-loaded
- under-saturated
- under-saturation
- under-titration
- underclay
- undercoat
- undercompacted
- undercompaction
- undercut slope