When you have to take a really bad shit, and you are farting to hold back the shits.
Also if someone says Winduku booku nuku, it is an even more extreme form of the phrase.
This one time my friend and I are on a train and the following conversation ensues,
"Dude did that guy who just left the bathroom take that really smelly shit?"
"Yeah man that shit was WINDUKU BOOKU!"
"My friend dicked me over for $50 the other day, not only was it Winduku Booku, it was fucking WINDUKU BOOKU NUKU!"