Definition of Plattdeutsch in English:

Plattdeutsch

noun & adjective

another term for Low German
‘The closest relatives to this language are Flemish, Dutch, and the Plattdeutsch dialects still spoken in Germany's Rhineland.’
another term for Low German
‘The term Plattdeutsch (sometimes translated as ‘Low German’) is used for the ‘broad’ dialects in the north and west.’

Origin

German, from Dutch Platduits, from plat ‘flat, low’ + Duits ‘German’.

Pronunciation

Plattdeutsch

/ˈplatdɔɪtʃ/