Sexual intercourse with a person who is unconscious or otherwise incapacitated. Dead logging is often accomplished after a long night of drinking by the dead loggee.
Legal experts sometimes refer to this activity as "rape".
#1: "Dude, I spent all this money buying Emily drinks all night and then she just passed out before I could even kiss her. I should've just dead logged the bitch!"
#2: "You should've WHAT????"
#1: "You know... in other words... RAAAAPE!"
#2: "JESUS CHRIST, JOSH!"