stealth

Concise Oxford English Dictionary © 2008 Oxford University Press:
stealth/stelθ/

▶noun

• 1 cautious and surreptitious action or movement.

• 2 [as modifier] (chiefly of aircraft) designed in accordance with technology which makes detection by radar or sonar difficult: a stealth bomber.

– origin ME (in the sense ‘theft’): prob. representing an OE word rel. to steal, + -th2.