What is a fish?

鱼是什么？

【复数】 fish或 fish.es
Any of numerous cold-blooded aquatic vertebrates of the superclass Pisces, characteristically having fins, gills, and a streamlined body and including specifically:
鱼：具有鳍、鳃和线形体型的冷血水生脊椎鱼纲动物中的任意一种并且尤指包括：
Any of the class Osteichthyes, having a bony skeleton.
硬骨鱼：有一套硬骨架的硬骨鱼纲中的一种
Any of the class Chondrichthyes, having a cartilaginous skeleton and including the sharks, rays, and skates.
软骨鱼：有一套软骨架的软骨鱼纲中的一种，包括鲨鱼、魟鱼和鳐鱼
The flesh of such animals used as food.
鱼肉：作食物用的此类动物的肉
Any of various primitive aquatic vertebrates of the class Cyclostomata, lacking jaws and including the lampreys and hagfishes.
鳗类，鳗：无颚的各种原始水生圆口纲脊椎动物中的一种，包括七鳃鳗和盲鳗
Any of various unrelated aquatic animals, such as a jellyfish, cuttlefish, or crayfish.
水生动物：与鱼无直接联系的水生动物，如海蜇、墨鱼或螯虾
Informal A person who is deficient in something:
【非正式用语】 笨蛋，生手：在某方面有不足的人：
a cold fish; a poor fish.
高傲自大的人；可怜虫
n.attributive.（