A monk is a person devoted to monastic and cloistered life, who is part of a religious order. The monastic tradition is present in various religions of the planet: Buddhism, Jainism, Taoism, Lamaism and Christianity are some of those who have followers who adopt monastic life.
Monk-mode refers to temporary self-imposed periods of increased discipline, usually entered into as self-improvement attempts. To 'go monk-mode' is to focus on work, routine, ritual, and strictly limit all sources of unproductive pleasure and distraction including but not limited to sexual gratification. Dopamine fasting is a related practice. Monk-mode has clear gendered connotations and an association with the Manosphere and Nofapper communities.