One of a series of recurring occasions, cases, essentially the same.
(obsolete) A piece of evidence; a proof or sign (of something). [16th-18th c.]
(computing) In object-oriented programming: a created object, one that has had memory allocated for local data storage; an instantiation of a class. [from 20th c.]
(massively multiplayer online game) A dungeon or other area that is duplicated for each player, or each party of players, that enters it, so that each player or party has a private copy of the area, isolated from other players.
(massively multiplayer online game) An individual copy of such a dungeon or other area.