invisible, subtle, blurred, feeble, inconspicuous, faint, indistinct, imperceptible, fuzzy, unnoticed, ill-defined, unseen, unwitnessed, undetected.
It will be a matter of no small difficulty to pilot him unobserved
through the city."
A glance at her watch showed that she had still a few moments in which to gain her room unobserved.
As the rector walked up and down the room, Dick was able to look upon his father's face unobserved.