undertint - variocoupler
- undertint
- undertread
- underutilization
- undervoltage
- undervoltage relay
- underwall
- underwashing
- underwater
- underwater concrete mix
- underwater drilling
- underwater manipulator
- underwater microphone
- underwater revetment
- underwater torch
- underweight
- underwing
- underwing carrier
- underwing rack
- undeveloped head
- undischarged