substitute word; placeholder term
A word used in place of another, often in grammar or linguistics contexts. Refers to a term that stands in for a more specific or appropriate expression.
Words like 'that' and 'it' are often used as substitute terms.
In this sentence, a placeholder word is used instead of a concrete noun.
Compound of 代用 (substitute, use in place of) and 語 (word, language). The term is transparently derived from its components.