1. (n.) 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.

2. (n.) 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.

3. (n.) 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.

arachnoid arbor vitae archipallium between brain brain stem cerebellar hemispheres cerebral cortex cerebrospinal fluid cerebrum convolution corpus callosum corpus striatum diencephalon dura mater endbrain fissure folia forebrain fornix frontal lobe glial cells globus pallidus gray matter gyrus hindbrain hippocampus hypothalamus lenticular nucleus limbic lobe little brain lobe mantle medulla oblongata meninges mesencephalon metencephalon midbrain myelencephalon neopallium occipital lobe optic chiasm pallium parietal lobe pia mater pineal body pituitary body pons reticular system rhombencephalon subthalamus telencephalon temporal lobe thalamus ventricle vermis white matter