noun

1. the soft, spongy tissue in the center of certain plant stems
2. the soft core of various other things, as of a bone or feather
3. the spongy, fibrous tissue lining the rind and surrounding the sections of an orange, grapefruit, etc.
4. the essential part; substance; gist
5. importance: now usually in of great pith and moment
6. Archaic strength; vigor; force

Etymology: ME pithe < OE pitha, akin to MDu pitte, pit of a fruit, kernel, pith of a tree

transitive verb

1. to remove the pith from (a plant stem)
2. to pierce or sever the spinal cord of (an animal) in order to kill it or make it insensible for experimental purposes