keyword

noun

1. a word that serves as a key, as to the meaning of another word, a sentence, passage, or the like.
2. a word used to encipher or decipher a cryptogram, as a pattern for a transposition procedure or the basis for a complex substitution.
3. Also called catchword. Library Science. a significant or memorable word or term in the title, abstract, or text of a document or other item being indexed, used as the index entry.
4. Digital Technology. a word used to classify or organize digital content, or to facilitate an online search for information: Search the database for the keyword “Ireland.”

noun

1. a word used as a key to a code
2. any significant word or phrase, esp a word used to describe the contents of a document