late autumn; late fall
Refers to the latter part of autumn, typically around November in modern usage. Can be used as a noun or adverbially.
The mountains in late autumn are beautiful with autumn leaves.
In late autumn, mornings and evenings get chilly.
ninth month of the lunar calendar
Archaic use referring to the ninth month of the traditional lunar calendar, roughly corresponding to October in the modern calendar. See also 長月.
See also: 長月
In the old lunar calendar, 晩秋 corresponds to the month of 長月.
秋口 refers to the start of autumn, whereas 晩秋 refers to the tail end of the season, just before winter.
From 晩 (late) + 秋 (autumn). The archaic lunar calendar sense derives from the traditional Japanese month names.