The act of reading things TOTALLY UNRELATED to what you’re SUPPOSED to be reading or doing, but -- these other things -- they're so damn interesting or maybe distracting but ... let’s face it: you’re off in the weeds and you know it.
A class in college designed specifically to fail students who are not good enough for a particular major. These courses usually have a high failure rate. The students who fail that class are "weeded" out of that major.