SummaryLinguistic expressions are very often indeterminate and have several possible readings. Syntactic indeterminacy may result from different underlying structures, from polysemous elements, or from so-called oscillation. Unlike the former two, oscillation cannot be reduced to one or more discrete interpretations in a given context, it is fundamentally non-resolvable. While oscillating structures do not hamper successful communication, they present a problem for linguistic analyses and categorizations. The relevant literature does not address oscillation systematically; if anything, it is treated in connection with problems of categorization. In this paper, oscillation is perceived as a phenomenonsui generis. We first give a definition of oscillation against the backdrop of other indeterminate structures and outline their relevance for a proper understanding of older and less formal varieties. Then we propose a tentative typology of oscillating structures and their potential triggers in selected Slavic languages.