Any of several small freshwater polyps of the genus Hydra and related genera, having a naked cylindrical body and an oral opening surrounded by tentacles.

(Greek mythology) A mythological serpent with many heads, slain by Hercules as one of his twelve labours.

plural of hydra

plural of hydra

a solitary polyp about 10 mm long, usually found attached to the under surfaces of water plants in ponds and streams. Similar to a sea anemone consisting of a hollow cylinder with a mouth surrounded by tentacles.

plural of freshwater hydra

(chemistry) An acid that does not contain any oxygen as opposed to an oxyacid; they are all binary compounds of hydrogen and a halogen or pseudohalogen.

plural of hydrangea

plural of hydracid

thinness of the blood