Just now, I came across the phrase "in flagrante" while reading a review of Paris Hilton's album Paris. You might ask what the fuck I was doing reading a review of an album by the embodiment of idiocy, immaturity, marketability and a whole host of STDs, but that's a discussion for another day.
Anyway, the sentence in question was the following:
Then she became infamous for shagging on video camera (and for taking a phone call while in flagrante).
You can infer its meaning in the above context, but my amusement was further piqued when I confirmed it:
'in blazing crime'; in the act of committing a crime or offence; in the act of having illicit sexual intercourse.
WP offers a more detailed definition.