noun
shunned character
In computing, a character that is deliberately avoided or excluded from use, often due to compatibility or security concerns.
このシステムでは、回避文字として特定の記号が使えない。
In this system, certain symbols cannot be used as shunned characters.
Compound of 回避 (かいひ, avoidance) and 文字 (もじ, character). The exact origin is uncertain; it is a technical term in computing.