cerebellum

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The trilobed structure of the brain, lying posterior to the pons and medulla oblongata and inferior to the occipital lobes of the cerebral hemispheres, that is responsible for the regulation and coordination of complex voluntary muscular movement as well as the maintenance of posture and balance.

Century Dictionary and Cyclopedia

1. n. The little brain or hind-brain of a vertebrate animal; a lobe of the brain developed on the dorsal side of the cerebrospinal axis, between the corpora quadrigemina in front and the medulla oblongata behind, and forming part of the roof of the fourth ventricle. The pons Varolii is the corresponding ventral portion of the cerebrospinal axis, and these two parts together are sometimes called the epencephalon. In man the cerebellum is a well-developed mass, having an average weight of about 5½ ounces, occupying the inferior occipital fossa, and separated from the posterior portions of the cerebral hemispheres above by the tentorium. A median portion or vermis and two lateral hemispheres are distinguished, and these are divided by transverse clefts into thin, closely packed laminæ. The cerebellum has three pairs of peduncles by which it is connected with the rest of the brain: the superior peduncles, which join it with the cerebrum; the middle peduncles, which pass down on either side to form the pons Varolii; and the Inferior peduncles or restiform bodies, which connect it with the medulla oblongata. The surface of the laminæ is of gray matter, while the interior is white, so that a section at right angles to the lamellæ presents a foliaceous appearance, which has received the name of arbor-vitæ. There are other masses of gray matter within, namely, the corpus dentatum, nucleus emboliformis, nucleus globosus, and nucleus fastigii. (See corpus and nucleus.) The cerebellum seems to he principally concerned with the coördination of voluntary movements. See cuts under brain and corpus.
2. n. In Insecta, the subesophageal ganglion, situated in the lower part of the head, and connected with the supra-esophageal ganglion or cerebrum by two nerve-chords surrounding the gullet

Wiktionary

1. n. neuroanatomy Part of the hindbrain in vertebrates. In humans it lies between the brainstem and the cerebrum. It plays an important role in sensory perception, motor output, balance and posture.

GNU Webster's 1913

1. n. (Anat.) The large lobe of the hind brain in front of and above the medulla; the little brain. It controls combined muscular action. See brain.

WordNet 3.0

1. n. a major division of the vertebrate brain; situated above the medulla oblongata and beneath the cerebrum in humans