What is Jiayou?
1.
A liternal translation from chinese is "fill more gasoline in your car".
Now general meaning is a friendly and cheerful shouting for encouraging athletes or players to have a better performance in competitions.
This word emerged in 2008 Summer Olympic games in Beijing.
e.g. When I heared the crowd shouted "Jiayou, jiayou, jiayou..." in stadium, I knew 100-meter final run began.
See