crack·er (n.)
1. A thin crisp wafer or biscuit, usually made of unsweetened dough.
2. One that cracks, especially:
2a. A firecracker.
2b. A small cardboard cylinder covered with decorative paper that holds
candy or a party favor and pops when a paper strip is pulled at one or both
ends and torn.
2c. The apparatus used in the cracking of petroleum.
2d. One who makes unauthorized use of a computer, especially to tamper with
data or programs.
3. Offensive:
3a. Used as a disparaging term for a poor white person of the rural,
especially southeast United States.
3b. Used as a disparaging term for a white person.
Gee, I wonder why you excluded definition 2d. You also omitted a more full
description, like the "Computing Dictionary" section under
http://www.hyperdictionary.com/dictionary/cracker. So what's the publish
date of that really old version of the Oxford's Dictionary that you have?
Since the computerese definition of cracker is over 2 decades old, looks
like it's time to buy a new version, or maybe head to the library and hope
they update it more often than twenty year intervals.