Undefined may refer to:
Mathematics Undefined (mathematics), with several related meanings Indeterminate form, in calculus
Computing Undefined behavior, computer code whose behavior is not specified under certain conditions Undefined value, a condition where an expression does not have a correct value Undefined variable, a variable that is accessed in code but has not been declared
Other uses Undefined, something that lacks any definition Undefined citizenship, a post-Soviet form of statelessness in Estonia
See also Null (disambiguation) Void (disambiguation) Invalid (disambiguation) Definition (disambiguation) Definable (disambiguation)