effused

Effused is the past tense and past participle of the verb effuse. It means to pour forth or emit something in a steady stream, such as a liquid or gas, or to spread through or over something in a diffuse manner. The term can describe physical phenomena, as well as ideas or feelings that are poured forth.

Origins and sense development: The verb comes from Latin effusus, the past participle of effundere, meaning "to pour forth" (ex- out + fundere to pour). In English, effuse retains a formal or literary tone and is often used in scientific or descriptive writing.

Scientific and medical usage: In physics and chemistry, effusion refers to gases escaping through a small opening; something effused may be said to have leaked or flowed out. In geology or volcanology, "effusive" describes lava that erupts as lava flows rather than pyroclastic explosions; "effused" lava or magma has emerged onto the surface. In medicine and pathology, an effusion is the accumulation of fluid in a body cavity or potential space; the phrase "blood effused" describes blood that has spread into surrounding tissue after an injury.

Usage and related terms: The word is relatively formal and somewhat archaic in everyday speech; alternatives such as emit, emanate, diffuse, or flow are often preferred. Related terms include effusion (the noun for the act or outflow) and effusive (an adjective describing outward emotion or lava that flows readily).