A person with the amazing ability to suck the vicinity completely clean of any productive attributes.
This is usually the result of an overwhelming lack of understanding combined with an extensive ability to confuse, but it can also be the result of being generally annoying in one way or another.
1 - Hey, how did the meeting go?
2 - Well, we made some great progress until Sarah appeared like an imploding star and turned the meeting into a black hole of logic and reasoning.
1 - again huh?
2 - yeah, we're back to discussing our main topic again