clandestine

adj

Etymology: From Latin clandestīnus (“secret, concealed”); compare French clandestin.

1. Done or kept in secret, sometimes to conceal an illicit or improper purpose.

   “clandestine military operations”

   “Monimia, who while she yielded to his earnest entreaties had always felt, from the natural rectitude of her understanding, the impropriety of their clandestine correspondence, would, he feared, be more than ever sensible of her indiscretion, when she found that a servant was entrusted with it...”

2. Not recognized as a regular member.