Kallisti!: From the Greek "Korristi". A Discordian greeting. Literally, "To the Prettiest One".
Flax: Discordian term for filthy lucre, i.e., Sirius Credits.
"Five tons of flax": The answer to deep philosophical questions, such as whether Zoners should be forced to wear RP straightjackets or not...
Cabbage: A non-believer. One lacking in Pineal acuity.
Pineal: A gland situated in the forehead, commonly associated with meditation and spiritual development.
Greyface: A person with a very limited reality tunnel. Seldom capable of thinking "outside the box".
23's: A Discordian "parting". Various sources. In ancient Morse code, the term for "break", or "break the line"; In the I Ching, Hexagram 23 is "Breaking Apart". (And of course 23 is a sacred Discordian number.)