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1.
Dicus is used to express surprise or astonishment, usually when something unexpected happens. It has overtones of indifference and ennui and is generally used in spur-of-the-moment situations.

Dicus is generally used only by pros, as it was invented by a pro. Lately though, it has become quite mainstream.

'Dicus' may be complemented with 'cactus', its cousin word, which basically means the same as 'shit', but is more versatile.

Dicus is basically interchangeable with OMG or OMFG.
"Man.... I got fired."

"Dicus. That's Cactus."
by John Cactus August 15, 2005