Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
sidelong [ˈsaɪdlɔŋ] adj косо́й
to give sb a sidelong glance смотре́ть*(посмотре́ть*perf) на кого́-н и́скоса
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
Русский: