Heah is used to replace any word in a sentence or is even used as a word all in its own. When used to replace a word in a sentence or conversation, the people conversing usually know each other well enough so that they can decipher what the word Heah is replacing. When used all in its own, Heah is usually yelled as a interjection word mid-sentence, either by the speaker or the listener. It is used in this manner usually as an attempt at humor.
"Oh my god go suck on a fatty HEAH!"
Heah meaning cock in this instance.
Example as an interjection -
"Hey Sean did you play that new video ga-HEAH!!!"