Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
sag [sæg] vi (breasts) отвиса́ть (отви́снуть perf) (roof, hem) провиса́ть (прови́снуть perf) (spirits, prices) па́дать (упа́сть*perf)
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
Русский: