michaelmas Meaning, Definition & Usage

  1. noun honoring the archangel Michael; a quarter day in England, Wales, and Ireland
    Michaelmas Day; September 29.

WordNet

Mich"ael*mas noun
Etymology
Michael + mass religious service; OE. Mighelmesse.
Definitions
  1. The feat of the archangel Michael, a church festival, celebrated on the 29th of September. Hence, colloquially, autumn.

Webster 1913