When you have to make a decision between someone you slept with or someone else.
Comes from the phrase "Blood is thicker than water"
Jill:I have to give a promotion between Joe or bob Alex:didn't you go out with joe?
Jill:yeah but bob is equally qualified for the job...
Alex: I say cum is thicker than water.
Also known as "Desi Water." Cheap beer such as Coors Light, Keystone Light, and very commonly Natural (Natty) Light or Ice. The term was coined by the Bro community as these so-called "beers" are the beverage of choice when the Bros take their lifted Ford Rangers, dirt bikes, and quads out to the desert for weekends of gasoline fumes, general drunkenness and groping of their underage female companions.
Bro #1: "Bro! Make sure we have enough Desert Water for this weekend in Glamis!
Bro #2: "Dude.... Bro... No worries! I've already got 6 cases of Natty Light!!"