furtively russian

• укра́дкой

  by stealth, stealthily, furtively

• подложи́ть

  lay, put, line, add, put some more, put furtively, plant (eg bomb)

• подкла́дывать

  lay, put, line, add, put some more, put furtively, plant (eg bomb)

• подгля́дывать

  peep, watch furtively, spy

• подгляде́ть

  peep, watch furtively, spy