| U.K. | United Kingdom |
| ult. | ultimately |
| Univ. | university |
| unkn. | unknown |
| Unnat. | unnatural |
| Unoffic. | unofficial |
| unstr. | unstressed |
| Urin. | urinary |
| U.S. | United States |
| U.S.A.F. | United States Air Force |
| U.S.S.R. | Union of Soviet Socialist Republics |
| usu. | usually |
| Utilit. | utilitarian |
