Natural Mangghuer texts exhibit a high rate of borrowing of lexical resources from Chinese. In this paper, I examine borrowings which are synonymous (or nearly so) with existing Mangghuer content words. I identify two different structural types of borrowings. Bound synonyms appear only as elements of compounds or fixed expressions, often in onomastic expressions or nouns that have a hyponymic relationship to an existing noun. Free synonyms are borrowed as independent words. Evidence from three disparate types of Mangghuer language data shows that any bound or free synonym may appear in nonce borrowings, idiosyncratic borrowings, or community-wide borrowings, a typology drawn from Poplack (2018). The data suggests that although nonce borrowing is probably common (resulting in nonce synonymy), many Chinese borrowings have become established to varying degrees in the speech community, with the result that Mangghuer has a greatly enriched vocabulary. In compiling an eventual lexicon of Mangghuer, speakers will have to make some difficult decisions about the formal documentation of borrowed synonyms whose use varies widely across the speech community.