Linguistics. (of a class of items) limited in membership and not readily expanded to include new items, as the class of inflectional affixes, articles, pronouns, or auxiliaries (opposed to open).
Hunting, Angling. restricted as to the kind of game that may be legally taken and as to where or when it may be taken:
woods closed to deer hunters.
(of a set in which a combining operation between members of the set is defined) such that performing the operation between members of the set produces a member of the set, as multiplication in the set of integers.
(of an interval) containing both of its endpoints.
(of a map from one topological space to another) having the property that the image of a closed set is a closed set.
(of a curve) not having endpoints; enclosing an area.
(of a surface) enclosing a volume.
(of a function or operator) having as its graph a closed set.