1843, "ancient obscene painting, especially in temples of Bacchus," from French pornographie, from Greek pornographos "(one) depicting prostitutes," from porne "prostitute," originally "bought, purchased" (with an original notion, probably of "female slave sold for prostitution"), related to pernanai "to sell," from PIE root *per- (5) "to traffic in, to sell" (see price (n.)) + graphein "to write" (see -graphy). A brothel in ancient Greek was a porneion.
In reference to modern works by 1859 (originally French novels), later as a charge against native literature; sense of "obscene pictures" in modern times is from 1906. Also sometimes used late 19c. for "description of prostitutes" as a matter of public hygiene. The "Medical Archives" in 1873 proposed porniatria for "the lengthy and really meaningless expression 'social evil hospital' ...."
I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description [hard-core pornography]; and perhaps I could never succeed in intelligibly doing so. But I know it when I see it, and the motion picture involved in this case is not that. [U.S. Supreme Court Justice Potter Stewart, concurring opinion, "Jacobellis v. Ohio," 1964]In ancient contexts, often paired with rhypography, "genre painting of low, sordid, or unsuitable subjects." Pornocracy (1860) is "the dominating influence of harlots," used specifically of the government of Rome during the first half of the 10th century by Theodora and her daughters. Pornotopia (1966) was coined to describe the ideal erotic-world of pornographic movies.
Books, photographs, magazines, art, or music designed to excite sexual impulses and considered by public authorities or public opinion as in violation of accepted standards of sexual morality. American courts have not yet settled on a satisfactory definition of what constitutes pornographic material. (See obscenity.)
Still and moving images, usually of women, in varying states of nudity, posing or performing erotic acts with men, women, animals, machines, or other props. Some say it degrades women, some say it corrupts young boys (who down-load it from the World-Wide Web or exchange it on floppy disks). Most of it is in the form of JPEG images. Many web sites offer porn of all sorts, almost always for a subscription. It is said that these are a driving force in the evolution of new technology and techniques for the web. Advertisments for them certainly constitute a significant proportion of all spam. There are even pornographic computer games, an early example being Mac Playmate.
Beware - many institutions, particularly universities, have strict rules against their computers and networks being used to transfer or store such things, and you might get corrupted.