Portmanteau words are terms which bring together elements of two (or occasionally more) existing words to create a new word. The best portmanteaus are exceptionally apt, and are able to convey ideas even to readers who've never seen them before. In articles about environmental issues, the term greenwash is easy to grasp, as it obviously combines "green" in the eco-friendly sense with "whitewash," meaning the glossing over or covering up of a misdeed. Typically, "greenwash" is used to describe government or corporate ploys to appear concerned about the environment when in fact environmental protection isn't a priority. Greenwashing is often associated with a publicity campaign, and magazine and newspaper content paid for by advertisers, lobbyists or interest groups is usually labelled advertorial (advertisement and editorial) or infomercial (like a commercial, but more informative).
We use portmanteau words every day without thinking. We complain about smog, stay in motels, get up late and eat brunch, and offer guesstimates when a more precise forecast isn't needed. We watch sitcoms on TV and take our girlfriends to rom-com movies. If a book or a movie is especially successful, it'll likely spawn not only sequels but also a prequel. Other common vocabularly mashups are chillax (something you hope to do on vacation), televangelist (televangelism now exists in Islam, Buddhism and other religions), gaydar (in case this word is unfamiliar to you, it means the ability many gay men and women possess to know if someone they've just met is also gay), and sexcapade. The last word, which needs no explanation, often appears in sensationalist reporting, especially in the UK.
At least two portmanteaus are derived from the adjective/noun "alcoholic" - shopaholic and chocaholic. A classic work of fiction inspired the newish term frankenfood (used by opponents of GM crops to describe the supposedly monstrous results of genetic modification). Heathcote Williams ranted against automobile culture and the thousands killed on the roads each year in his 1991 poem Autogeddon, a portmanteau title borrowed a few years later by singer-songwriter Julian Cope for his car-themed album.
The internet has given us a flood of portmanteaus. Web users are known as netizens, while companies reach out to employees and potential customers through webinars (online seminars). Concerts, speeches and other public events are often webcast.
Writers and broadcasters like to use portmanteau terms because they're snappy and trendy. Some, however, have fallen out of use. Only those who followed the news in the early 1970s will remember that the dismal combination of high inflation and economic stagnation then prevalent was referred to as stagflation. If your personal economic circumstances don't allow for travel to distant places, consider a staycation, a vacation spent at home!
Young people are constantly creating new portmanteaus, and some of these neologisms gain a foothold in the English language. Marijuana aficionados have been known to describe anything which is as enjoyable as smoking their favorite drug, or which is better appreciated when under its influence, as bongtastic (a bong, if you don't know, is a kind of pipe used to smoke marijuana).
The adjective fagalicious, mostly but not exclusively used by those who dislike homosexuals, means flamboyantly gay. Now that homosexual lifestyles are mainstream in several Western nations, the words gaydar (the ability many gays have to detect a person's sexual orientation long before they declare it) and gayby (a baby raised by a gay couple) are well known.
English isn't the only language to employ portmanteau words. In Japanese, young people with few career ambitions who drift from one temporary job to another, often backpacking through southeast Asia or Australia between periods of employment, are known as freebeiter - a term which blends the English "free" with part of the German word "arbeit" (a verb and noun meaning "work").