help--what is a "nonce"?

I learned a new word today, but I can't seem to get a sense of the meaning, which makes the amateur philologist in here crazy.

OED gives: 1.a. for the nonce. a. For the particular purpose; on purpose; expressly. Freq. with infinitive or clause expressing the object or purpose. In quot. 1949: for the purpose of teasing or joking; for its own sake. Now Eng. regional (south.) and Sc.

and

1.c. For the particular occasion; for the time being, temporarily; for once.

So a google "define: nonce" gives the above and also: A randomly chosen value, different from previous choices, inserted in a message to protect against replays

The only definition I found which does make sesne is a secondary definition in OED:

(british criminal slang) nonce: A sexual deviant; a person convicted of a sexual offence, esp. child abuse

Ah here's a fun column from william safire in the new york times (which, by the way, you'll probably have to register for a free account in order to view) in which he says: "Today’s linguistic space odyssey shows how mainstream readers can tangle with the weaving Web. A last word: Don’t knock yourself out looking for the origin of e-maelstrom, “a storm of electronic communications.” It was minted today, right here, and if it does not die in the nonce, a dispute will arise over capitalization."

Ha--okay, I get that.

Any of you use this word? And how?