stationary message source; stationary information source
Technical term in information theory and computing, referring to a source that emits messages with a probability distribution that does not change over time.
The entropy of a stationary information source does not depend on time.
Compound of 定常 (stationary, steady) + 情報 (information) + 源 (source). The term is a direct calque from English 'stationary information source' used in information theory.