a cardinal number, three plus one.

a symbol of this number, 4 or IV or IIII.

a set of this many persons or things.

a playing card, die face, or half of a domino face with four pips.

fours, Jazz . alternate four-bar passages, as played in sequence by different soloists

with guitar and piano trading fours.

Automotive .

an automobile powered by a four-cylinder engine.

the engine itself.

amounting to four in number. ?

on all fours. all fours ( def. 3 ) .

adjective

quadrigeminal , quadripartite , quadrivial , quadruple , quadruplicate , quaternary , quaternate , tetrad

noun

quadrigeminal , quadripartition , quadrivium , quadrumvirate , quadruple , quadruplet , quadruplets , quartet , quartette , quaternary , quaternion , quaternity , tetrad , tetralogy

verb

quadrisect