Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
experimental [ɪkspɛrɪˈmɛntl] adj (methods, ideas) эксперимента́льный; (tests) про́бный
at the experimental stage на ста́дии экспериме́нта
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
Русский: