n. The act of pouring out, literally or figuratively; a shedding forth; an outpour: as, the effusion of water, of blood, of grace, of words, etc.n. That which is poured out; a fluid, or figuratively an influence of any kind, shed abroad.n. Specifically An outpour of thought in writing or speech; a literary effort, especially in verse: as, a poetical effusion: commonly used in disparagement.n. In pathology, the escape of a fluid from the vessels containing it into a cavity, into the surrounding tissues, or on a free surface: as, the effusion of lymph.n. [ML. effusio(n-), tr. of Gr. ῤν/σις.] That part of the constellation Aquarius (which see) included within the stream of water. It contains the star Fomalhaut, now located in the Southern Fish.