n.any of numerous fishes of the class Chondrichthyes characterized by a cartilaginous skeleton and placoid scales: sharks; rays; skates
同义词：elasmobranch
英汉双解大词典
selachian/sɪˈleɪkɪən/
1.
ADJ（形容词）
of, relating to, or belonging to the Selachii (or Elasmobranchii), a large subclass of cartilaginous fishes including the sharks, rays, dogfish, and skates 板鳃类的
2.
N（名词）
any fish belonging to the subclass Selachii 板鳃类鱼