Not open to participation by non-members or the public.

(computing) A testing arrangement in which a beta test version of software is distributed to a small group of testers.

The display of text on a television or video screen, usually a transcription of the audio portion of a program as it occurs (either verbatim or in edited form), most frequently used by the deaf and language learners. Closed captions are encoded invisibly, and displayed by a decoder.

(simile, colloquial) miserly, tight, or secretive

An enclosed precinct surrounding a cathedral.

plural of closed book

unreceptive to new ideas or information; not open to any agreement.

(topology) A set whose complement is open.

(algebra, field theory, of a field) Which contains as an element every root of every nonconstant univariate polynomial definable over it (i.e., over said field).

crowded tightly together