IPA: /ˌsuːpəˈskrɪpʃən/
KK: /ˌsuːpərˈskrɪpʃən/
A written note or title placed above or outside of something else, often used in contexts like prescriptions or inscriptions.
The superscription on the envelope indicated it was a special delivery.
Superscription is formed from "super-" (meaning above or over) and "scriptio" (from "scribere", meaning to write). The word refers to something that is written above or on top of something else.
Think of something that is 'written above' ('super-') — that's what superscription means.