The Collaborative International Dictionary of English v.0.48:

Kernel \Ker"nel\, n. [OE. kernel, kirnel, curnel, AS. cyrnel,
   fr. corn grain. See Corn, and cf. Kern to harden.]
   1. 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; as, the kernel of a nut. See Illust. of
      Endocarp.
      [1913 Webster]

            'A were as good crack a fusty nut with no kernel
                                                  --Shak.
      [1913 Webster]

   2. A single seed or grain; as, a kernel of corn.
      [1913 Webster]

   3. A small mass around which other matter is concreted; a
      nucleus; a concretion or hard lump in the flesh.
      [1913 Webster]

   4. The central, substantial or essential part of anything;
      the gist; the core; as, the kernel of an argument.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Kernel \Ker"nel\, v. i. [imp. & p. p. Kerneledor Kernelled;
   p. pr. & vb. n. Kerneling or Kernelling.]
   To harden or ripen into kernels; to produce kernels. Kerneled

WordNet (r) 3.0 (2006):

kernel
    n 1: the inner and usually edible part of a seed or grain or nut
         or fruit stone; "black walnut kernels are difficult to get
         out of the shell" [syn: kernel, meat]
    2: a single whole grain of a cereal; "a kernel of corn"
    3: the choicest or most essential or most vital part of some
       idea or experience; "the gist of the prosecutor's argument";
       "the heart and soul of the Republican Party"; "the nub of the
       story" [syn: kernel, substance, core, center,
       centre, essence, gist, heart, heart and soul,
       inwardness, marrow, meat, nub, pith, sum, nitty-
       gritty]

The Free On-line Dictionary of Computing (19 January 2023):

kernel
kernal

   (Note: NOT "kernal").

   1.  The essential part of Unix or other
   operating systems, responsible for resource allocation,
   low-level hardware interfaces, security etc.  See also
   microkernel.

   2.  An essential subset of a programming language,
   in terms of which other constructs are (or could be) defined.
   Also known as a core language.

   (1996-06-07)