<p><strong>Noun</strong></p><ul><li>the season between summer and winter; fall. In the Northern Hemisphere, it is from the September equinox to the December solstice; in the Southern Hemisphere, it is from the March equinox to the June solstice.</li><li>a time of full maturity, especially the late stages of full maturity or, sometimes, the early stages of decline: to be in the autumn of one's life.</li></ul>