A feature of many word processing, page layout, and other text-based programs that checks the spelling of each word of a document and compares it to that of words included in a dictionary. Words it cannot verify the spelling of are flagged for the user. Many programs allow the user to add specialized terms or proper names that may not be included in the default dictionary. Spelling checkers should be used with care; they are incapable of finding words that become other words when misspelled. Also referred to as spell checkers, and the term spell-check has become a verb meaning "to proofread a document using a spelling checker."