Combination of Shitty and Sense. In otherwords, bullshit. A clandestine manner of telling someone they are full of shit.
After smiling and noding at your superior's instructions for some time, this person finally comes to a conclusion. Instead of telling this person they are full of shit you say, with a straight face, "Yes sir, that makes perfect shense"
Someone who just told a very bad joke can be said to have a very good shense of humor.