Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
underground [ˈʌndəgraund] adv (work) под землёй
adj (car park) подзе́мный; (newspaper, activities) подпо́льный
n
the underground (BRIT) (railway) метро́ nt ind; (POL), подпо́лье
to go underground (fig) уходи́ть*(уйти́*perf) в подпо́лье
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
Русский: