- unmapped petroleum initially in place
- unmeasurability of absolute direction of space
- unmeasurability of absolute position of space
- unmeasurability of absolute time
- unmeasurability of direction of time flow
- unmeasurable
- unmixed
- unmixed domain
- unmixed ideal
- unmixedness theorem
- unmixed ring
- unmoderated
- unmodulated
- unmodulated groove
- unmount
- unmovable cultural relics
- unmyelinated nerve fibre
- unnamed number
- Unnamed Society
- unnatural amino acid
- unnatural base
- unnatural death
- unnatural nucleotide
- Unnelling and Underground Space Technology
- unnotched