cyst
/sɪst/noun
1- Biology a thin-walled hollow organ or cavity in an animal or plant, containing a liquid secretion; a sac, vesicle, or bladder【生】（动、植物）孢囊; 囊胞。
1.1
- Medicine a membranous sac or cavity of abnormal character in the body, containing fluid【医】囊肿。
1.2
- a tough protective capsule enclosing the larva of a parasitic worm or the resting stage of an organism（寄生虫幼虫或生物静止期的）包囊。
词源
early 18th cent.: from late Latin cystis, from Greek kustis 'bladder'.