a chemotactic substance, identical with cAMP, secreted by myxamebas of cellular slime molds and attracting other myxamebas to aggregate and form a pseudoplasmodium.
Origin: 1945–50; < NL Acras(iales) an order of cellular slime molds (Acras(is) a genus, so named from the lack of fusion between the cells (< Gk; see a-6, crasis) + -ales-ales) + -in2
[uh-krey-sin] 
sɪn