An exclamation used in particularly bad circumstances. Typically followed by the expression "Thanks for nothing," used in a saracastic fashion, even if the speaker has no apparent audience or reason to be displeased with the person to whom he/she is speaking. Commonly used among 5-year-olds with undiagnosed attention deficit disorder or attention deficit hyperactivity disorder, frustrated office workers and people who dislike the word shit because of its pedestrian nature.
John S.: Mrs. Johnson, my mom needs a cup of flour to bake a cake.
Mrs. Johnson: Well, honey, I'm sorry but we just ran out of flour. Please tell your mommy I'm sorry.
John S.: Shithorn! Thanks for nothing!
Pronounced as two words, "shit horn", this means your ass, especially when you're eating foods that are very flatogenic, like curry.
That Goan curry is really making my shithorn blow sour notes!