A portmanteau or portmanteau word is a new word formed by joining two other words and combining their meanings. It is a linguistic blend of two words. Portmanteaus had their genesis from the intention of emphasizing more than one idea or concept through a single word. The word Portmanteau is derived from the French word portmanteau, combined from porter (to carry) and manteau (mantle). While these words originated in 16th century, Lewis Carroll is credited with coining the word portmanteau. The word portmanteau was first used in this sense by acclaimed English writer Lewis Carrol in the book ‘Through the Looking-Glass’ (1871), in which Humpty Dumpty explains to Alice the coinage of the unusual words in "Jabberwocky", where slithy means "slimy and lithe" and mimsy is "miserable and flimsy".

Let us have a look at a few common portmanteaus.

1. Motel from motor and hotel

A motel is a roadside hotel designed primarily for motorists, typically having the rooms arranged in low blocks with parking directly outside

2. Infotainment from information and entertainment

Infotainment is a type of media that tries to combine educational or useful information and entertaining content.

3. Fantabulous from fantastic and fabulous

Fantabulous means extremely fine or desirable; excellent; wonderful.

4. Docudrama, from documentary and drama

A docudrama is a genre of radio and television programming, feature film, and staged theatre, which features dramatized re-enactments of actual events.

5. Breathalyzer, from breath and analyzer

A breathalyzer or breathalyser is a device for estimating blood alcohol content (BAC) from a breath sample. 

6. Gamestorming, from games and brainstorming

Gamestorming is a set of practices for facilitating innovation in the business world. A facilitator leads a group towards some goal by way of a game, a structured activity that provides scope for thinking freely, even playfully.

7. Guesstimate, from guess and estimate

Guesstimate is defined as an estimate made without using adequate or complete information, or, more strongly, as an estimate arrived at by guesswork or conjecture.

8. Imagineering, from imagination and engineering

Imagineering is the implementation of creative ideas in practical form.

9. Workaholic, from work and alcoholic

A workaholic is a person who works compulsively. While the term generally implies that the person enjoys their work, it can also alternately imply that they simply feel compelled to do it.

10. Advertainment from advertising and entertainment

Advertainment is a term used to reflect the intertwining relationships between advertising and entertainment. Typically it refers to media that combines various forms of entertainment with elements of advertising to promote products or brands.

11. Telemarketing, from telephone and marketing

Telemarketing is a method of direct marketing in which a salesperson solicits prospective customers to buy products or services, either over the phone or through a subsequent face to face or Web conferencing appointment scheduled during the call.

12. Advertorial, from advertising and editorial

An advertorial is an advertisement in the form of editorial content.

13. Skyjacking from sky and hijacking

Aircraft hijacking is the unlawful seizure of an aircraft by an individual or a group. In most cases, the pilot is forced to fly according to the orders of the hijackers.

14. Stagflation, from stagnation and inflation

In economics, stagflation is a situation in which the inflation rate is high, the economic growth rate slows, and unemployment remains steadily high. It raises a dilemma for economic policy, since actions designed to lower inflation may exacerbate unemployment, and vice versa.

15. Beautility from beauty and utility

Beautility is the quality of having aesthetic merits while serving a practical purpose, especially of an industrial design.

16. Intercom, from internal and communication

An intercom is a stand-alone voice communications system for use within a building or small collection of buildings, functioning independently of the public telephone network.

17. Mechatronics, from mechanical and electronics

Mechatronics is a multidisciplinary field of engineering that includes a combination of mechanical engineering, robotics, electronics, computer engineering, telecommunications engineering, systems engineering and control engineering.

18. Electrocute from electric and execute

Electrocution is death or serious injury caused by electric shock, electric current passing through the body.

19. Camcorder, from camera and recorder

A camcorder is an electronic device originally combining a video camera and a videocassette recorder.

20. Emoticon, from emotion and icon

An emoticon, is a pictorial representation of a facial expression using characters—usually punctuation marks, numbers, and letters—to express a person's feelings or mood, or as a time-saving method.

It can be seen that the meanings of all portmanteaus are apparent from the combination. Most of these words will not be found in standard dictionaries. But portmanteaus are very commonly used in English language, particularly in modern parlance.