stealthy

adjective

slow, deliberate, and secret in action or character
intended to escape observation : furtive
designed to produce a very weak radar return

Wiktionary

Pronunciation: /ˈstɛlθi/ / /ˈsʈɛːl.d̪iː/ / /ˈsʈɛːl.t̪hiː/

adj

Etymology: Etymology tree English stealth Proto-Indo-European *-kos Proto-Germanic *-gaz Proto-West Germanic *-g Old English -iġ Middle English -y English -y English stealthy From stealth + -y.

Characterized by or resembling stealth or secrecy.
“stealthy military manoeuvres”