The act of simultaneously masturbating and crying your eyes out. This is usually due to depression and desire for sexual companionship. Although not necessary to fall under the category, some find it useful and economically efficient to use their tears has a substitute lubricant AKA slippery sauce.
My imaginary girlfriend died last night so I sadfapped till' the morrow.
Pronounced with excessive exaggeration of the second "a", as in example 1. Shaddap is used to tell somebody to shut up without sounding overly serious. It can also be used pre-emptively, as in example 2. The crowning usage of shaddap however is as an unexpected end to a phrase, particularly when used to imply that somebody had said something extremely stupid.
1. "Shaddaaaaaaaaaaaap."
2. "I know what you're going to say, and I'm telling you, shaddap."
3. "How much more does a hard drive weigh when full?"
"Oh it weighs about shaddaaaap."