euthanize
verb [ I or T ] (UK usually euthanise) uk/ˈjuː.θə.naɪz/ us/ˈjuː.θə.naɪz/
（对动物实施）安乐死
to kill an animal because it is very old or sick or because there is no one to take care of it
Overcrowded shelters would not be able to euthanize unwanted animals. 拥挤不堪的动物救助站无法对被遗弃动物实施安乐死。