It is when someone says they're going to take a bath but they just turn on the water and wet their hair. You can tell by the fact that the towels are dry, the mirror is clean, and the sink and their clothes may be wet because they were too lazy to take of their top and dip their head in the running water. Can also be seen in public bathroom/shower areas.
Tiara says she takes a shower every day but I went in and she pulled a bathtub hoax.
by Jane-etter Eno November 09, 2007
Theorem which proves that the masses can and will be manipulated for comedic purposes.
"Look at the suntanned people pouring out of that church -- it's a bathtub hoax."
by as cheap as toasters December 03, 2004