A yee haw (also stylized as "yee-haw"), is a person who is of southern decent, or rural area who talks in heavy southern accent. Also can be used in speech as a northerner making fun of someone of southern decent.
"James, quit being a yee haw", "sorry there partner".
"After an upsetting third place at the Iowa caucus, Howard Deanmade an unforgettable yee haw that was played around 700 times on CNN within the next 24 hours."