[ sɪst ]
■ noun
1》 Biology a thin-walled hollow organ or cavity in an animal or plant, containing a liquid secretion.
2》 Medicine a membranous sac or cavity of abnormal character in the body, containing fluid.
3》 a tough protective capsule enclosing the larva of a parasitic worm or the resting stage of an organism.
Origin
C18: from late L. ~is , from Gk kustis 'bladder'.