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!"[1][2]
In the terminology of phonetics, the raspberry has been described as a voiceless linguolabial trill, transcribed [r̼̊] in the International Phonetic Alphabet,[3] and as a buccal interdental trill, transcribed [ↀ͡r̪͆] in the Extensions to the International Phonetic Alphabet.[4]