Hidden things can't be seen — they're concealed in some way. A hidden video camera inside a teddy bear might secretly be keeping an eye on a new babysitter.

People with hidden feelings don't let their sadness, anger, and joy show; and hidden clues in a treasure hunt can't be easily found. Hidden things can be obscured deliberately (like hidden eggs at an Easter egg hunt), or simply out of view or undetected by you. Hidden is the past participle of hide, from the Old English hydan, which means "to hide or conceal," but also "to bury a corpse."

Definitions of hidden

adj not accessible to view

concealed, out of sight
invisible, unseeable
impossible or nearly impossible to see; imperceptible by the eye

adj designed to elude detection

“a hidden room or place of concealment such as a priest hole”
hidden on any grounds for any motive

adj difficult to find

hidden valleys”
“a hidden cave”
hidden on any grounds for any motive

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