B.F.o.t.D.
The thing your body does when it decides to be annoying and do it right when you're in the middle of something.
My B. F. o. t. D. hit me during a test and I had to write my answer in the bathroom.
I was trying to text my friend, but my B. F. o. t. D. took over.
My B. F. o. t. D. happened at the worst time during my favorite show.