Sesshin (接心) is sometimes described as 攝(摂)心, and it means concentration of a confused heart. It also means to mind the feelings.
Sometimes it is also called as Sesshinfuran. In Yuikyogyo (the last Buddhist teaching made by Shakyamuni), there is a description which says 'Joto Sesshin Zaishin' (常当摂心在心, literally, always to be Sesshin).
In the Zen sect, Sesshin means to do a meditation, have the spirit focus on one subject, and not to be distracted. Later in the Zen sect, people came to use the word Sesshin especially to describe an ascetic practice in which a person constantly does a meditation for a certain period of time regardless of day and night.
In Shinjoen, which is said to be one of the new religions that branched out from the traditional Buddhism, doing meditation and manas regarding the behavior and belief of the everyday life based on the 'spiritual word' given by a medium is called 'Uso Sesshin.'
In addition, exemplifying the given spiritual word in everyday life and social activities is called 'Muso Sesshin.'