A portmanteau is a linguistic blend of words, where parts of two or more words are combined to create a new word that retains meanings from both. For example, "brunch" is a portmanteau of "breakfast" and "lunch." Portmanteaus are often used to describe new concepts, trends, or phenomena in a concise way. The term itself originally referred to a suitcase with two compartments, symbolizing the merging of different elements.