A screamer is a distinctive headline which has been written with the goal of drawing attention to the article beneath it. While all headlines arguably serve this function, screamers demand attention, insisting that readers turn to the article in question immediately and without delay. Screamers are typically sensational, and sometimes specifically designed to be provocative. For some good examples of screamers, peruse the tabloids at the checkout stand, which often have a plentiful array of screamers to choose from.
Screamers appear on the front page, because the idea is to entice consumers into buying the newspaper or magazine to read what's inside. In newspapers, screamers are always above the fold, ensuring that they will be visible, and they are often larger than the surrounding headlines so that they really stand out. Screamers may also be italicized or underlined for extra effect, and some companies also allow the use of punctuation marks in screamers; exclamation points, for example, will really make a screamer stand out.
This term is most commonly used in print journalism, in reference to newspaper and magazines. Screamers also appear in online journalism, however, and at more adventurous sites, they may literally scream at the viewer, with the use of an embedded sound file. Screamers also show up on television, in the scrolling news feeds at the bottom of some network feeds. Urgent breaking news may show up as a screamer while the network prepares to cut to a journalist, for example, ensuring that viewers stay pinned to the network for an update.
Some newspapers eschew the screamer, preferring a more stately and elegant look; the New York Times is probably the most famous for its staid, unremarkable appearance. More stately papers prefer descriptive headlines which sum up the content of an article, like "Politician X Speaks at Union Rally," allowing readers to get a quick idea of the coverage on the front page, while screamers highlight the sensational content of a news item, as in "Politician X Claims 'Oil Companies Should be Nationalized'."
Writing a screamer, or any headline, takes talent. Headlines need to be succinct, clear, and to the point, and editors need to be careful about unintentional double entendres and glaring mistakes such as the infamous "Dewey Defeats Truman" headline of 1948, which the Chicago Tribune may never live down. In the case of a screamer, more journalistic license is involved, and the editor may generate a headline which punches up tension to draw the eyes.