The same Meaning as the word "yeah" or "yes" but "Hyeah" is used to portray sarcasm or to take the piss as a joke. Also it can be said to mean a definite yes.
Bob: Want 100 pound for your birthday?
Used when describing America or more specifically Texas. It should be spoken with a strong Texas accent. Use often during akward silences. Shows pride in your country...America
Jim: Hey Bill did you know McDonalds is expanding to India
Bill: Hyeahs AMERICA!
Phrase used by emo kids because apparently it's too conformist to say "yes". This is also done with a flick of the hair that'll cover one deformed eye. Although originally taken from credible goths, the emos have made it their own. This is also an attention seeking tactic as are all their pathetic actions....
*Done in gay feminine generic american voice-"Dude; i hate these attention seekers dude... i mean they are all so wrapped up in their jobs and public opinion; that if they could even open their minds for one second they'd be scared of the freedom that i experience; yknow??? Conformists, all of them.... <b>Hyeah</>"