"Ǒu chū" is a verb meaning "to vomit out"—that is, to forcefully expel stomach contents through the mouth. The first character 呕 (ǒu) means "to vomit" and carries the core physiological action; the second character 出 (chū) means "out" or "to emerge," indicating direction and completion. Together, they form a resultative verb compound emphasizing the outward expulsion of material from the body. This phrase is more specific and vivid than the simpler verb 呕 (ǒu) alone, highlighting both the action and its directional result.

It’s commonly used in medical contexts, health descriptions, or narrative accounts of illness, food poisoning, or strong emotional reactions (e.g., disgust or shock). While grammatically neutral, it tends to appear in formal reports, clinical notes, or descriptive writing rather than casual speech—where people often prefer simpler alternatives like 吐 (tǔ) or 呕吐 (ǒu tù). It can take objects (e.g., 呕出鲜血) and frequently appears with aspect markers like 了 or 过 to indicate completed or experienced action.