| unseemly | vergonzoso |
| unseen | no visto |
| Unseen character | Personaje fantasma |
| Unseen University | Universidad Invisible |
| unselfish | altruista |
| unselfish person | altruista |
| unselfishness | altruismo |
| unserious | chistoso |
| unserviceable | inútil |
| unsettle | perturbar |
| unsettled | indeciso |
| unsettling | inquietante |
| unshackle | dispensar |
| unshackles | excento |
| unshakable | imperturbable |
| unshakeable | inquebrantable |
| unshapely | deforme |
| unshaven | sin afeitar |
| unsheltered | a la intemperie |
| unshorn | intonso |
| unshrinking | intrepido |
| unsightly | de aspecto desagradable |
| unskeptical | ingenuo |
| unskilled | inexperto |
| unskilled worker | bracero |
| unskillful | desgraciado |
| unsmilingly | seria |
| unsociable | insociable |
| unsold | no vendido |
| unsolicitous | voluntario |
| unsolvable | insoluble |
| unsolved | sin resolver |
| Unsolved problems in biology | Problemas no resueltos de la biología |
| Unsolved problems in mathematics | Problemas no resueltos de la matemática |
| Unsolved problems in physics | Problemas no resueltos de la física |
| unsophisticated | sencillo |
| unsorted | sin ordenar |
| unsound | poco saludable |
| unsounded | falso |
| unsparing | liberal |
| unspeakable | indecible |
| unspecified | no especificado |
| unspoiled | no contaminado |
| unspoilt | no contaminado |
| unspoken | tácito |
| unstable | variable |
| Unstable star | Estrella inestable |
| unstableness | inestabilidad |
| unstably | erratil |
| unsteadily | flojo |
| unsteadiness | inseguridad |
| unsteady | variable |
| unsterilizable | no esterilizable |
| unstinting | generoso |
| unstop | destapar |
| unstoppable | incontrolable |
| Unstructured Supplementary Service Data | USSD |
| Unstrut | Río Unstrut |
| Unstrut-Hainich | Unstrut-Hainich-Kreis |
| unstuck | despegado |
