OXFORD DICTIONARY
autumn, n.
1 the third season of the year, when crops and fruits are gathered, and leaves fall, in the N. hemisphere from September to November and in the S. hemisphere from March to May.
2 Astron. the period from the autumnal equinox to the winter solstice.
3 a time of maturity or incipient decay.
autumn crocus any plant of the genus Colchicum, esp. meadow saffron, of the lily family and unrelated to the true crocus.
ME f. OF autompne f. L autumnus
THESAURUS
autumn
aestival, arctic, autumnal, boreal, brumal, canicular, equinoctial, fall, harvest, harvest home, harvest time, hibernal, hiemal, midsummer, midwinter, out of season, seasonal, solstitial, spring, springlike, summer, summerlike, summerly, summery, vernal, winter, winterlike, wintery, wintry
ROGET THESAURUS
autumn
Evening
N
evening, eve, decline of day, fall of day, close of day, candlelight, candlelighting, eventide, nightfall, curfew, dusk, twilight, eleventh hour, sunset, sundown, going down of the sun, cock-shut, dewy eve, gloaming, bedtime, afternoon, postmeridian, p, m,
autumn, fall, fall of the leaf, autumnal equinox, Indian summer, St. Luke's summer, St. Martin's summer, midnight, dead of night, witching hour, witching hour of night, witching time of night, winter, killing time, vespertine, autumnal, nocturnal, midnight, the outpost of advancing day, sable-vested Night, this gorgeous arch with golden worlds inlay'd.