Mundari, an Austroasiatic language of India (Munda family), has often been cited as an example of a language without word classes, where a single word can function as noun, verb, adjective, etc. according to the context. These claims, originating in a 1903 grammar by the missionary John Hoffmann, have recently been repeated uncritically by a number of typologists. In this article we review the evidence for word class fluidity, on the basis of a careful analysis of Hoffmann's corpus as well as substantial new data, including a large lexical sample at two levels of detail. We argue that in fact Mundari does have clearly definable word classes, with distinct open classes of verb and noun, in addition to a closed adjective class, though there are productive possibilities for using all as predicates. Along the way, we elaborate a series of criteria that would need to be met before any language could seriously be claimed to lack a noun-verb distinction: most importantly strict compositionality, bidirectional flexibility, and exhaustiveness through the lexicon.