'Sea horse' definitions:

Definition of 'sea horse'

noun

Either of two large northern marine mammals having ivory tusks and tough hide over thick blubber [syn: walrus, seahorse, sea horse]

noun

Small fish with horse-like heads bent sharply downward and curled tails; swim in upright position [syn: seahorse, sea horse]

From: GCIDE

Sea horse \Sea" horse`\
1. A fabulous creature, half horse and half fish, represented in classic mythology as driven by sea dogs or ridden by the Nereids. It is also depicted in heraldry. See Hippocampus. [1913 Webster]
2. (Zool.) (a) The walrus. (b) Any fish of the genus Hippocampus. [1913 Webster]
Note: In a passage of Dryden's, the word is supposed to refer to the hippopotamus. [1913 Webster]

From: GCIDE

Hippocampus \Hip`po*cam"pus\, n. [L., the sea horse, Gr. ? a hippocampus (in senses 1 and 2); "i`ppos horse + ? to bend.]
1. (Class. Myth.) A fabulous monster, with the head and fore quarters of a horse joined to the tail of a dolphin or other fish (Hippocampus brevirostris), -- seen in Pompeian paintings, attached to the chariot of Neptune. --Fairholt. [1913 Webster]
2. (Zool.) A genus of lophobranch fishes of several species in which the head and neck have some resemblance to those of a horse; -- called also sea horse. [1913 Webster]
Note: They swim slowly, in an erect position, and often cling to seaweeds by means of the incurved prehensile tail. The male has a ventral pouch, in which it carries the eggs till hatched. [1913 Webster]
3. (Zool.) A name applied to either of two ridges of white matter in each lateral ventricle of the brain. The larger is called hippocampus major or simply hippocampus. The smaller, hippocampus minor, is called also ergot and calcar. [1913 Webster]