There are multiple definitions - click on the translation that matches your context.

titkosít

ige

full

classify

verb

Definitions of classify

to put things or people into particular groups based on their qualities or features

The Dewey Decimal System has been used to classify books in libraries for 140 years.

to state or determine that something is secret and cannot be accessed for security reasons

None of the WikiLeaks material was classified higher than "Secret".