keyword

noun

1. Any word used as the key to a code.
2. Any word used in a reference work to link to other words or other information.
3. Any important word in a text or document, which may be linked to other words or other information, or listed in the metadata for searches to find.
4. A reserved word used to identify a specific command, function, etc.

   “Each function has an entry address which must be quoted after the USR keyword.”

   “Since C++11, the auto keyword is used to tell the compiler to deduce the actual type of a variable that is being declared from its initializer.”

5. Any word that occurs in a text more often than normal.

verb

1. (transitive)To tag with keywords, as for example to facilitate searching.

   “Besides being able to search the photography collections, of which 3,000 images have been scanned in so far, the feature is meant to provide a more subjective and spontaneous way for visitors to view the art: browsing images, looking at them sequentially and keywording, or tagging, them for themselves and other viewers.”