| in a fog(expression, idiom, concealment) |
| in disguise(expression, idiom, adverb, concealment, furtively) |
| in hiding(expression, idiom, concealment) |
| in secret(expression, idiom) |
| in the background(expression, idiom, mysterious, reticent, taciturn) |
| intelligence(adjective, secret, hidden, spy, covert) |
| invisible |
| masked(obscure, secret, unknown, hidden, concealed) |
| mystical(adjective, secret, unknown, hidden, underground) |
| on the QT(expression, adjective, idiom, adverb, dishonest) |
| quiet |
| recondite(secret, unknown, hidden, underground, concealed) |
| shifty(dishonest, cunning, deceitful, sneaky, underhanded) |
| shrouded(obscure, secret, unknown, hidden, clandestine) |
| slinking(secret, private, hidden, sneak, sneaky) |
| slinky(sneak, skulking) |
| sneak(clandestine, underground, undisclosed, skulking) |
| sub-rosa(adjective, dishonest, cunning, deceitful, secret) |
| subterranean |
| swathed |