It is when a girl is having sex and keeps quacking like a baby duck. Then her sex partner eats food and regurgitates the food into the girls mouth or pussy or bum. If it is in the bum they shit it out into sex partners mouth. If in the mouth they eat it. If in the pussy the sex partner licks it out.
(n) also known as quack, quax0r and quackulus0r
A crappy math class that forces you to sit down for several hours and do integration, derivative-atives, and all-around boring crap.
(v) the act of studying (for) the above noun
Adam and I had to do quackulus for 13 hours until we barfed voluminously.