<p><strong>Noun</strong></p><ul><li>a word that serves as a key, as to the meaning of another word, a sentence, passage, or the like</li><li>a word used to encipher or decipher a cryptogram, as a pattern for a transposition procedure or the basis for a complex substitution</li><li>Also called catchword</li><li>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</li><li>Digital Technology: a word used to classify or organize digital content, or to facilitate an online search for information</li></ul>