A question. Your voice rising as you complete its pronounciation. Depending on the situation, one could be asking, "What?" or perhaps, "Pardon?" or virtually any other inquiry.
2) "Hat." Pronounced with a tone of finality. An expression of comprehension. "I understand," or, "Yes, I concur."
3) "You're a hat." Spoken with disdain. An expression of dislike for the individual referred to. In this instance, it could take the place of "goon," "mouth-breathing ignoramus," "degenerate," or any number of alternate degrading remarks.
4) Additionally, "hat" can be used as a prefix or suffix attached to other words, altering and enhancing the specificity of their meanings. Most commonly, this is done to add humour and effect to insults.
Examples include, but are not limited to: asshat, hatsack, fuckhat, hatboat, and Dumpy McHatfuck.
2) "We just lost the big game to Calgary! Hat!"
3) "Don't be such an hat."