The article examines capabilities of Russian zoophonic verbs (those describing sounds produced by animals) to create semantic modifications. Using the appending inventory of zoophonic verbal modifications from novel sources, previously unused in lexicographic practices, the open (infinite) nature of semantic modifications' domain, its composition and the fluidity of its lacuna zones are shown. The structure of zoophonic verbal modifications is examined; verbal modifiers, non-typical for this lexical-semantic group of verbs, are inventoried. The obstacles to successful production of semantically modified derivatives during different stages of synthesis are classified by several criteria: denotative, semantic, and distributive. The research findings demonstrate the peculiarities of Russian zoophonic verbs' behavior as well as map out their modification capabilities during the process of synthesis.