The act of searching medical websites to match real or imagined symptoms in oneself or ones friends and family. This automatically makes the searcher a medical expert and this person is usually known for their hypochondriac tendencies and uncanny abilities to drive you nuts.
Woman A: (cough) "I'm not feeling so hot."
Woman B: "Do you have shortness of breath and a fever?"
Woman A: "Mayyyybe.... I feel a little warm..."
Woman B: "Let me do some internet diagnosing on WebMD....Oh my god!! You have Pneumonoultramicroscopicsilicovolcanoconiosis! We've gotta get you to the emergency room!"