Blowing a raspberry

Blowing a raspberry, razzing or making a Bronx cheer, is to make a noise similar to flatulence that may signify derision, real or feigned. It is made by placing the tongue between the lips and blowing.

A raspberry (when used with the tongue) is not used in any human language as a building block of words, apart from jocular exceptions such as the name of the comic-book character Joe Btfsplk. However, the vaguely similar bilabial trill (essentially blowing a raspberry with one's lips) is a regular consonant sound in a few dozen languages scattered around the world.

Spike Jones and His City Slickers used a "birdaphone" to create this sound on their recording of "Der Fuehrer's Face", repeatedly lambasting Adolf Hitler with: "We'll Heil! (Bronx cheer) Heil! (Bronx cheer) Right in Der Fuehrer's Face!"

In the terminology of phonetics, the raspberry has been described as a voiceless linguolabial trill, transcribed in the International Phonetic Alphabet, and as a buccal interdental trill, transcribed  in the Extensions to the International Phonetic Alphabet.

Name
The nomenclature varies by country. In most anglophone countries, it is known as a raspberry, which is attested from at least 1890, and which in the United States had been shortened to razz by 1919. In the United States it has also been called a Bronx cheer since at least the early 1920s.