ausstülpen

Ausstülpen is a German verb describing the act of turning a part of the body or a structure inside out or outward, i.e., to evert or evaginate. The process involves making the inner surface or interior become exterior, or pushing a part to the outside. The term is primarily used in technical contexts such as anatomy, zoology, botany, and embryology, where it can describe natural developmental processes, physiological responses, or surgical manipulation that causes tissue to be turned outward. The corresponding noun Ausstülpung refers to the act or result of such a process; in related disciplines, terms like eversion or evagination are commonly used as equivalents, though exact usage depends on the field and tradition.

In everyday language, ausstülpen can also mean turning a container part inside out—for example turning a sleeve or a pocket outward—but in scientific contexts the focus is on biological structures.

Etymologically, the word combines aus- (out) with Stülpen (to pull over, to turn inside out). It is a Fachterminus in German, employed to specify outward reversal of orientation in a precise, technical sense.