Hidra
1. Hidra, Vodna kača
trouble that cannot be overcome by a single effort because of its many aspects or its persistent and pervasive quality [težava, ki je ni mogoče premagati s posameznim naporom zaradi njenih številnih vidikov ali vztrajne in povsod prisotne kakovosti.]
2. Hidra
(Greek mythology) monster with nine heads; when struck off each head was replaced by two new ones [(Grška mitologija) pošast z devetimi glavami; ko se je glava odsekala, sta zrasli dve novi.]
3. Hidra, Vodna kača
a long faint constellation in the Southern Hemisphere near the equator stretching between Virgo and Cancer [dolga, neizrazita ozvezdje na južni nebesni polobli, blizu ekvatorja, ki se razteza med Devico in Racom.]