Merriam-Webster Collegiate Dictionary - ur-

 I. combining form  or uro-  Etymology: New Latin, from Greek o~, ouro-, from ouron urine, from ourein to urinate — more at urine  1. urine uric  2. urinary tract urology  3. urinary and urogenital  4. urea uracil  II. combining form  or uro-  Etymology: New Latin, from Greek o~, ouro-, from oura tail — more at ass tail uropod  III. prefix  Usage: often capitalized  Etymology: German, from Old High German ir-, ~ thoroughly (perfective prefix) — more at abide  1. original ; primitive ~form  2. original version of urtext  3. prototypical ; arch- ~anticommunist