(idiomatic) Seemingly hidden, but actually not hidden and easy to find.

(taxation) A tax that is not visible to the consumer at the point of retail, having been levied on intermediate products, such as inputs to a finished product, or outputs from raw material production.

A statistical Markov model in which the system being modelled is assumed to be a Markov process with unobserved (hidden) states.

past participle of hide away

(aviation) A connecting city between the origin and destination of a passenger flight, where a passenger can save money on the airfare by disembarking at the connecting city rather than continuing to the destination.

plural of hidden city

Most deeply hidden.

(computing, Internet) Deep Web

(baseball) A fielding play where the fielders deceive the baserunners as to the location of the ball, allowing one of the fielders to attempt to tag a runner out without the runner being aware of it.

plural of hidden variable