noun
May-December romance; couple with older man and younger woman
A somewhat dated term for a romantic relationship between an older man and a younger woman, often implying a significant age gap. The word evokes the image of twilight (夕暮れ) suggesting the later stage of life for the man.
あの二人は夕暮れ族だと言われている。
They say those two are a May-December couple.
年の差婚 is a more modern and neutral term for a marriage with a large age gap, without the specific older-man-younger-woman connotation of 夕暮れ族.
Compound of 夕暮れ (twilight) and 族 (tribe, group), coined to describe couples where the man is in the 'twilight' of his life. The exact origin is uncertain, but it likely emerged in Japanese media in the late 20th century.