From Tekkenpedia

Poison Knee Taunt
Command	1+2+3+4~b,f,u,d+3+4
Stance
Damage	25,1
Hit Range	m!
Properties	CS JG

Poison Knee Taunt is a secret move for Yoshimitsu in Tekken 5 and Tekken 5: Dark Resurrection and the opponent must be Bryan Fury. This move is a mimic of the move Fury Taunt which shows Bryan lifting his knee and then waving his fist while laughing. A major difference is that instead of laughing Yoshimitsu exhales bad breath.