Laughing out quiet loudly. It's when something's funny so you laugh out quietly (let's be honest how many of us actually laugh out loud) but do it loudly because it deserves more than quiet laughing. Remember, it's not the same as laughing out loud; it's laughing out quite loudly.
B2o4b1 - Did you hear about Dave? He got pwned by two bouncers at the bar for being too drunk.