returnummer
Returnummer is a term without a widely established definition in major reference sources. The form appears to blend the English word “return” with the suffix "-nummer" found in several Germanic languages, which means “number.” Because there is no standard meaning attached to returnummer itself, its interpretation depends on context, and it may simply be a misspelling or a nonce word.
In sports contexts, if used, returnummer would most plausibly refer to a jersey or back number—the number
In logistics or e-commerce contexts, one could construe returnummer as a “return number” used to track returned
Because returnummer lacks a widely agreed definition, readers should rely on the surrounding text to infer