Go ahead, treat yourself. Check out the latest chick flick, get a bikini wax or enjoy an ice cream that might give you a brain freeze.

And if you're not sure what you're getting yourself into, it might be wise to consult the latest edition of Merriam-Webster's Collegiate Dictionary (search) which formally defines those terms that have taken root in American conversation.

The words are joined by 15 other new entries that make up the 1,664 pages of the newly published book. So if you're not interested in movies meant to appeal to women, discreet hair removal procedures or running the risk of feeling a sudden shooting pain in the head caused by ingesting very cold food, maybe there's another endeavor to catch your fancy.

Try steganography, the "art or practice of concealing a message, image, or file within another message, image, or file." That may not be the latest craze among hobbyists, but it's an activity that caught the attention of Merriam-Webster's lexicographers.

"We have editors who spend a part of each day reading magazines and newspapers, looking for evidence of how words are being more commonly used," said John Morse, Merriam-Webster's president and publisher. "We're looking for words that show up in the contexts that the average adult might encounter."

The new words offer explanations of emerging technologies and careers, thereby reflecting changes and developments in American society. You could try your hand at being a cybrarian (a person who finds, collects, and manages information available on the Internet,) or as a hospitalist ("a physician who specializes in treating hospitalized patients of other physicians in order to minimize the number of hospital visits by other physicians.")

The Springfield-based dictionary publisher has an ongoing list of about 17 million words it monitors. Every year, a few of them make it into print, followed by a succinct definition. Once a decade, the Collegiate Dictionary is completely rewritten, with some old words tossed out to accommodate the influx of about 10,000 of the latest nouns, verbs and adjectives. The last rewrite was done in 2003.

It takes about 10 years for a promising word to get into the dictionary from the time it first gets noticed. But some have a speedy rise to Merriam-Webster legitimacy, depending on the urgency of their meaning and impact

Among this year's fastest climbers is SARS, the acronym for the severe acute respiratory syndrome that began making headlines just two years ago with an outbreak in China.

"That was enough of a public health concern to get it in the dictionary right away," Morse said. "Now, one of two things could happen. Either we'll never hear about SARS again, and if so, I've wasted three lines of type in the dictionary. Or it will come back, and everyone will go to the dictionary in a time of need to see how SARS is defined."

Merriam-Webster is also recognizing civil unions, which have been talked about enough in social and political circles to earn a place in the Collegiate's latest edition.

The dictionary dates the term's genesis to 1992. But a Vermont lawmaker insists it wasn't really coined until 2000, when his state became the country's first to establish the legal rights of same-sex couples.

"We needed to decide a name for this, and we just didn't have one," said Bill Lippert, a Democrat who now chairs the Legislature's House Judiciary Committee. "Somewhere, someone said `civil union,' and we all said `oh, that sounds good.' It was a name that did what we wanted it to do. It was new, it designated that the fact that this was a civil act, and it suggested the bringing together of a union."

Others terms seem like they've been a long time coming.

Merriam-Webster traces the bikini wax's origins to 1985, and some spa owners say it's about time the hair-removal procedure made it into the dictionary.

"Bikini waxes are now old hat," said Shannon Fluery, owner of the Brooks and Butterfield Day Spa in Northampton, where as many as 40 women come in for a bikini wax each week. "It's not such a taboo as it used to be. People wouldn't talk about it too much and just did them at home. But salons have definitely picked up on them, and now they're very, very common."

At last, Merriam-Webster agreed.

Following is a partial list of new words and their definitions being entered into this year's edition of Merriam-Webster's Collegiate Dictionary.

Amuse-bouche (noun): a small complimentary appetizer offered at some restaurants.

Battle dress uniform (noun): a military uniform for field service.

DHS (abbreviation) : Department of Homeland Security.

Hazmat (noun): a material (as flammable or poisonous material) that would be a danger to life or to the environment if released without precautions.

Metadata (noun): data that provide information about other data.

Otology (noun): a science that deals with the ear and its diseases.

Retronym (noun): a term consisting of a noun and a modifier which specifies the original meaning of the noun. ("Film camera," for instance).

Tide pool (noun): a pool of salt water left (as in a rock basin) by an ebbing tide, called also tidal pool.

Wi-Fi (certification mark): used to certify the interoperability of wireless computer networking devices.

Zaibatsu (noun): a powerful financial and industrial conglomerate of Japan.