<p><strong>Noun</strong></p><ul><li>A cardinal number, three plus one.</li><li>A symbol of this number, 4 or IV or IIII.</li><li>A set of this many persons or things.</li><li>A playing card, die face, or half of a domino face with four pips.</li><li>Fours, Jazz: alternate four-bar passages, as played in sequence by different soloists: with guitar and piano trading fours.</li><li>Automotive: an automobile powered by a four-cylinder engine; the engine itself.</li></ul><p><strong>Adjective</strong></p><ul><li>Amounting to four in number.</li></ul>