Sesh is a colloquial or slang short form of session, (plural seshes), and is also a short form of seisiun, a word used by the Irish. Generally, sesh refers to a period of time spent engaged in some group activity. Increasingly, it has come to mean, particularly among young people, an informal, often impromptu, get-together or meeting to perform a group activity, usually with an element of excitement or air of conviviality. Although a sesh may or may not have a defined goal to accomplish, it generally encompasses an implicit goal of a social bonding experience.
In Ireland, sesh is used colloquially as short for seisiun, which is a term that has been used by the Irish for centuries, particularly with regard to music played in pubs. In the UK and Australia and Ireland, sesh also refers to a period of sustained social drinking. Sesh began appearing more commonly in print during World War II. By the 1980s sesh appeared in the middle-class culture of British youths. Today a music festival in the UK offers original live music nights called The Sesh at Kingston upon Hull.
Since World War II, the use of the word sesh has expanded beyond the UK and Australia, to the United States, likely precipitated by the exposure of US soldiers to their UK and Australian comrades. Since at least the 1960s, sesh has been used in the US to describe a gathering of musicians to perform or jam together. Today, sesh is often used in the US in conjunction with sports activities performed in or before a small group, particularly extreme sports; for example, skate sesh, surf sesh and snowboard sesh. A search of Google and of YouTube videos for the word "sesh" further evidences the word having entered the vernacular.
The word sesh is often coupled with a prefacing descriptive term, which can be either a noun or a verb, to describe the particular type of group activity or get-together. For example, jam sesh is often used to refer to musicians gathering together and playing without extensive preparation or prearrangements. Skate sesh, rail sesh, ramp sesh and street sesh are phrases used by the youth skateboarding subculture to describe skateboarding activities, typically performed with or before a small group of friends. More generally, morning sesh, afternoon sesh, and Sunday sesh are used to describe get-togethers or activities at certain times. Stoners also use the word 'sesh' to refer to smoking marijuana with a group of people (e.g. chill sesh). The word sesh is also used alone to refer to a particular type of activity in the context that is understood by a group's members.