The day of the week before Tuesday and following Sunday. Recorded from Old English (in form Mōnandæg), the name originally meant ‘day of the moon’, a translation of late Latin lunae dies.
Monday club a right-wing political club, formed in 1961, that originally held its meetings on Mondays.
Monday morning quarterback in North America, a person who passes judgement on and criticizes something after the event, an armchair critic.
Saint Monday used with reference to the practice among workmen of being idle on Monday, as a consequence of drunkenness on the Sunday, chiefly in the phrase to keep Saint Monday.