noun
a reversible, emulsoid stage existing between the sol and gel formations, in which the addition of a third substance causes the separation of the sol into two immiscible liquid phases: an essential stage in the formation of proteins, antibodies, etc.
Origin:
ME coacervacioun, a heaping together < L coacervatio < coacervatus, pp. of coacervare, to heap up < co- (see com-) + acervare, to form a heap < acervus, a heap