彻查 is a compound verb meaning 'to thoroughly investigate' — implying a complete, rigorous, and often official examination of facts, causes, or responsibilities. The first character 彻 (chè) means 'thorough', 'penetrating', or 'to the end', while 查 (chá) means 'to check', 'to examine', or 'to investigate'. Together, they emphasize depth and completeness: not just a cursory look, but an exhaustive inquiry into all relevant aspects.

This term is commonly used in formal, official, or journalistic contexts — especially when serious incidents occur, such as safety accidents, corruption cases, public health crises, or major policy failures. It often appears in government statements, news reports, or investigative journalism, carrying connotations of accountability and transparency. While it can be used transitively (e.g., 彻查此事), it's frequently paired with nouns like 原因 (cause), 责任 (responsibility), or 事件 (incident) to specify what is being investigated.