How odd. I only have two dictionaries in my house to look it up in (one old abridged Websters and an unabridged Random House), but I managed to find it in both of them; however, it lists it spelled as two separate words; no wonder your dictionary cannot find a single word spelled that way.
- Random House Compact Unabridged Dictionary (Copyright © 1996, 1993, 1987 by Random House, Inc.)
fair´ din´kum, Australian. dinkum.
din•kum (ding´kum), adj. Australian. genuine; authentic. [1890-95 of obscure orig.] - Webster's New Collegiate Dictionary (Copyright © 1979 by G. & C. Merriam Co.)
¹din•kum \'ding-kum\ adj [pro. fr. E dial. dinkum, n., work] Austral: authentic, genuine
²dinkum adv, Austral: truly, honestly - http://dictionary.reference.com
Incidentally, just for fun, I looked up colour in my two dictionaries and you'll never guess what I found: it was in
both of them!
Perhaps I know of the term because I'm old; perhaps it's because I read books (it's used occasionally in fictional books). It's certainly not an obscure English word/phrase...and certainly not at all difficult to look up in any dictionary.
I have three questions: Why are you fighting over "fair dinkum" and "color vs. colour"? Are you professional English-language grammarians? And if you are, what does that have to do with mIRC (which is demonstrably international)?