surreptitious (adjective) surreptitious: sneaky, secret
Sinonime: clandestine,
covert,
fraudulent,
furtive,
hidden, hole-and-corner, hush-hush, on the QT, on the sly,
private, skulking, slinking,
sly, sneaking,
stealthy, sub-rosa, unauthorized, under wraps, under-the-table, undercover, underhand, veiled
Antonime: aboveboard, authorized,
honest,
open