hydra

n. 水螅、九頭蛇、難以根除之禍害

學術名詞

水螅：動物學、生命科學、地質學
長蛇[星]座：天文學
長蛇座：海事

英文釋義

trouble that cannot be overcome by a single effort because of its many aspects or its persistent and pervasive quality
small tubular solitary freshwater hydrozoan polyp