Middle Dutch is a collective name for a number of closely related West Germanic dialects whose ancestor was Old Dutch. Wikipedia

West Germanic dialects, 1150–1500, ISO 639 language codes Wikipedia Disambiguation

West Germanic language of the High and Late Middle Ages Wikidata

A language of the Netherlands and Belgium, the ancestor of Modern Dutch. 1150-1500 AD. OmegaWiki

Collective name for a number of closely related West Germanic dialects (whose ancestor was Old Dutch) which were spoken and written between 1150 and 1500 in the present-day Dutch-speaking area. There was at that time as yet no overarching standard language, but they were all mutually intelligible. Wiktionary

The Middle Dutch language. Wiktionary (translation)