secret

Entry Definition
secret agent, infiltrator, spy, counterspy; anyone working in secret
they have secret dealings with each other, they reach secret agreement, they collude
s/he acts in secret, clandestinely
h/ secret spot, h/ place (e.g., secret fishing hole or berry-picking place)
s/he tells h/ to be tight-lipped, tells h/ to keep secret what is said; s/he tells h/ in no uncertain terms, tells h/ strictly