尽悉 is a formal, literary verb meaning 'to fully understand' or 'to comprehend completely.' It combines 尽 (jìn), which conveys 'exhaustively' or 'to the utmost,' and 悉 (xī), meaning 'to know thoroughly' or 'to be well acquainted with.' Together, they emphasize complete, deep, and often deliberate comprehension—not just surface-level awareness but thorough grasp of details, implications, or underlying truths.

This term appears frequently in official documents, legal texts, academic writing, and formal speeches. It carries a tone of seriousness and authority, rarely used in casual conversation. While grammatically it functions as a transitive verb (e.g., 尽悉情况), it’s often followed by abstract nouns like 原因, 内情, 实情, or 背景. Learners should note that 尽悉 is not interchangeable with everyday verbs like 知道 or 了解; it implies a level of mastery or exhaustive insight appropriate to high-stakes or institutional contexts.