A Flash Washer is someone in your office that briefly runs their hands (sometimes just fingers) under the water after using the restroom. Basically stating that their restroom activity did not warrant a soap and warm water hand washing.
I'm not eating anything that Donna brings to the pot luck on Thursday, she's a Flash Washer.
This is when you are on the phone having a personal conversation at work when all of the sudden, the office gets so quiet that you think you've been "left behind". The reality is that your coworkers are in the office, sitting quietly at their desks, listening to your conversation.
"Hey, let me call you back. I thought an Office Rapture occurred but I think everyone just heard me tell you that I think my boss is a bitch."