jack block
When you're trying to jack off and someone or something stops you cold, like your dad won't shut up on the computer or your mom decides to walk in and ask for a snack.
My dad won't leave the computer, and I'm stuck with a hard-on and no porn.
I tried to jack off, but my little brother walked in and said, 'Hey, wanna play video games?'.
I got halfway through my session and my mom walked in and said, 'I'm making cookies.'