stealthily (adverb) covertly: clandestine, underhandedly
Sinonime: by stealth, clandestinely, furtively, hush-hush, in camera, in holes and corners, on the QT, on the quiet, on the sly, privately,
secretly, slyly, stealthily, sub rosa,
surreptitiously, under wraps, undercover, wildcat
Antonime: candidly, frankly,
honestly, openly, overtly, publicly