kernel

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A grain or seed, as of a cereal grass, enclosed in a husk.
• noun The usually edible seed inside the hard covering of a nut or fruit stone.
• noun The central or most important part; the core.
• noun A small amount of something, especially when potentially developing into something else.

from The Century Dictionary.

• To crenelate.
• noun The edible substance contained in the shell of a nut or the stone of a fruit.
• noun Technically, in botany: In phanerogams, strictly, the whole body of a seed within the coats, namely, the embryo, and, when present, the albumen.
• noun In pyrenomycetous fungi, in old usage, all of the soft parts of the pyrenocarp or perithecium within the firm outer wall. In both these senses a synonym of nucleus.
• noun A gramineous seed with its husk or integument; a grain or corn: as, a kernel of wheat, oats, or maize: formerly applied also to the seed of the apple and other pulpy fruits.
• noun The bundle of fat on the fore shoulder; any swelling or knob of flesh.
• noun Figuratively — The central part of anything; a mass around which other matter is concreted; a nucleus in general.
• noun The important part of anything, as a matter in discussion; the main or essential point, as opposed to matters of less import; the core; the gist: as, to come to the kernel of the question.
• To harden or ripen into kernels, as the seeds of plants.
• noun An enlarged lymphatic gland.
• noun In metallurgy, a nucleus of a double sulphid of copper and iron obtained in roasting cupriferous iron pyrites. The kernels are separated by hand from the lumps of pyrites and are melted for copper.
• noun A battlement.

from the GNU version of the Collaborative International Dictionary of English.

• noun The essential part of a seed; all that is within the seed walls; the edible substance contained in the shell of a nut; hence, anything included in a shell, husk, or integument. See Illust. of endocarp.
• noun A single seed or grain.
• noun A small mass around which other matter is concreted; a nucleus; a concretion or hard lump in the flesh.
• noun The central, substantial or essential part of anything; the gist; the core.
• intransitive verb To harden or ripen into kernels; to produce kernels.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The core, center, or essence of an object or system.
• noun The central (usually edible) part of a nut, especially once the hard shell has been removed.
• noun A single seed or grain, especially of corn or wheat.
• noun US The stone of certain fruits, such as peaches or plums.
• noun computing The central part of many computer operating systems which manages the system's resources and the communication between hardware and software components.
• noun mathematics, algebra Those elements, in the domain of a function, which the function maps to zero.
• noun mathematics The set of members of a fuzzy set that are fully included (i.e., whose grade of membership is 1).

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the choicest or most essential or most vital part of some idea or experience
• noun a single whole grain of a cereal
• noun the inner and usually edible part of a seed or grain or nut or fruit stone