noun
implementation-defined
Computing term used in specifications to indicate that a behavior is left to the implementer's discretion, not fixed by the standard.
C言語では、char型の符号の有無は実装者定義である。
In C, whether the char type is signed or unsigned is implementation-defined.
Compound of 実装者 (implementer) and 定義 (definition), calque of English 'implementation-defined'.