This article examines cross-Strait variation in Chinese baseball terminology through a document-based comparison of two primary sources: the terminology appendix contained in the Chinese Taipei Baseball Association’s baseball rules and the China Baseball Association’s Basic Terminology of Baseball standard. Based on Supplementary Dataset S1, a cleaned 363-entry English-Chinese comparison dataset, the study investigates how baseball terms differ across the Strait in documentary coverage, lexical designation, expression style, and communicative relevance. The analysis identifies 214 directly comparable entries with renderings on both sides. Of these, 101 are classified as convergent or near-convergent, while 113 show lexical divergence. A further 149 entries do not enter the directly comparable subset. The findings show that cross-Strait baseball terminology is shaped by more than isolated word-level difference. Taiwan-side terms often preserve compact and conventionalized forms used in baseball practice, whereas Mainland standardized forms frequently display a more explicit and institutionally codified style. The article argues that such variation should not be treated simply as inconsistency, but as specialist-language variation shaped by different historical, institutional, and communicative conditions. On this basis, the article suggests a graded, communication-oriented approach that tolerates low-sensitivity variants, cross-references moderate-sensitivity terms, and coordinates high-sensitivity rule terms for umpiring, commentary, translation, and instruction.