Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
undecided [ʌndɪˈsaɪdɪd] adj (person) нереши́тельный*нереши́телен (question) нерешённый
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
Русский: