1. (n.) A narrow opening, a crack; a cleft; as, the fissure of a rock\.

2. (v. t.) To cleave; to divide; to crack or fracture.

abysm abyss amputate arachnoid arbor vitae archipallium arroyo ax between brain bisect box canyon brain stem breach break break open break up breakage broach burst bust butcher caesura canyon carve cavity cerebellar hemispheres cerebellum cerebral cortex cerebrospinal fluid cerebrum cessation chap chasm check chimney chink chip chop cleave cleft cleuch clough col come apart come unstuck convolution corpus callosum corpus striatum coulee couloir crack cranny crevasse crevice cut cut away cut in two cut off cut open cwm defile dell dichotomize diencephalon dike disintegrate dispart dissever ditch divaricate divide donga draw dura mater endbrain excavation excise exfoliate fall to pieces fault flaw flume fly open folia forebrain fornix fracture frontal lobe furrow gap gape gash give away give way glial cells globus pallidus gorge gray matter groove gulch gulf gully gyrus hack halve hew hiatus hindbrain hippocampus hole hypothalamus incise incision interim intermission interruption interval jigsaw joint kloof lacuna lance lay open leak lenticular nucleus letup limbic lobe little brain lobe lull mantle medulla oblongata meninges mesencephalon metencephalon midbrain moat myelencephalon neopallium notch nullah occipital lobe ope open open up opening optic chiasm pallium pare parietal lobe part pass passage pause pia mater pineal body pituitary body pons prune ravine rend rent reticular system rhombencephalon rift rime rip rive rupture saw scale schism scissor scissure seam separate sever slash slice slit slot snap snip splinter split spread spread out spring a leak spring open start subthalamus sunder suspension swing open tap tear tear open telencephalon temporal lobe thalamus throw open trench valley ventricle vermis void wadi white matter whittle