A rare or archaic term for a bilingual person or someone who studies bilingualism.
From 'bilingual' + '-ist' (suffix meaning a person who practices or specializes in something), following the pattern of 'linguist' and similar agent nouns.
The '-ist' suffix is powerful—it turns adjectives into people ('bilingual' becomes 'bilinguist'), which is how English creates job titles and descriptions of specialized people!
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