Gerund functioning as a lexical noun meaning 'the act of moving stealthily'.
Synonyme
stealthy movement
furtive behavior
sneakinggerundium / partizip präsens More precise classification than generic ADJECTIVE.
The sneaking cat approached the bird quietly.
Крадущийся кот тихо подошел к птице.
He had a sneaking suspicion that something was wrong.
У него было подкрадывающееся подозрение, что что-то не так.