Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
sponge [spʌndʒ] n гу́бка#; (also: sponge cake) бискви́т
vt (wash) обтира́ть (обтере́ть*perf) гу́бкой
vi
to sponge off or on sbсиде́ть*(impf) на ше́е у кого́-н
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.