headword; entry word
Refers to the word or phrase that is defined in a dictionary entry; a technical term used in lexicography.
In dictionaries, headwords are often displayed in bold.
見出し語 specifically means the headword entry itself in a dictionary, while 項目 in this sense refers more generally to the entry or item within a reference work.
status keyword
Compound of 見出し (みだし, 'heading, index') + 語 (ご, 'word').