A portmanteau or portmanteau word is a linguistic blend of words, in which parts of multiple words, or their phones (sounds), and their meanings are combined into a new word.

A portmanteau should be distinguished from a compound, which does not involve the truncation of parts of the stems of the blended words. For instance, starfish is a compound, not a portmanteau, of star and fish; whereas a hypothetical portmanteau of star and fish might be stish.

Other Examples of a Portmanteau:

telephone + marathon = telethon

medical + care = Medicare

parachute + troops = paratroops

camera + recorder = camcorder

web + log = blog

breakfast + lunch = brunch

spoon + fork = spork

costume + play = cosplay

More Info: en.wikipedia.org