Used before or after a stunt to alert others, relieve pressure, generate more force, and express excitement. It is a sound coming from someone that is in a state of high adrenaline, which is expected during MTB stunts.

There are many functions of YYEEEEWWWW:

  1. To alarm others
  2. Clear your mind before a big trick
  3. Show of and attract attention
  4. A sense of habit
  5. Tension control

Although many have chosen to adopt the word YYEEEEWWWW, there are many synonyms including: YEAH, WOO, YEHAW, BRAPPP, *WHISTLE* etc.

(Thanks to Brainy Bikers – Why do Mountain Bikers Say YEW, for the concise definition)