What is a word? There has been a recent renewal of interest in correspondences between syntactic and prosodic constituents within languages (for example, Selkirk’s 2011 paper on Match Theory). However, there is little consensus in the literature on how to define prosodic constituents of different types. This talk focuses on two common definitions of the “prosodic word”: a syntactic definition defines a prosodic word by correspondence to a syntactic constituent, while a phonological definition defines a prosodic word by phonological properties. Drawing on data from Blackfoot (an Algonquian language spoken in Alberta and northern Montana), I show that these two kinds of definitions do not always coincide. There are two “word-like” phonological domains in Blackfoot, one of which corresponds to a syntactic definition of the word, and one of which corresponds to a phonological definition of the word. At the end of the talk I explore implications of this research for future investigation into issues at the prosody-syntax interface.