It can be used as a noun, a pronoun, an adjective, a verb, an adverb, a preposition, a conjunction, and an interjection. Though teachers may not acknowledge it as a real word, it will be printed in dictionaries worldwide soon enough.
Its true origin may never be known, but it was brought back in 2009 by a 16-year-old and his friends with too much time on their hands.
Billy: Miss, what are you gyamming about?
Teacher: Is that a note?!
Billy: I think you're gyammed, Miss. I don't have anything!
Creepy Guy on Street: You there! Come over here! NOW!
Kid: Gyamyos! *runs away*
Guy 1: Yo, what time do you have?
Guy 2: A quarter past gyam.
Guy 1: What? Seriously, what time is it?
Guy 2: Alright, fine, it's gyam o' clock.
Guy 1: Dude, come on! I have to go soon!
Guy 2: Alright, gyam, it's 3:30.
Kid 1: Are you coming to the party tonight?
Kid 2: I can't, my mom's gyamming...
Person 1: Gyamyos.
Person 2: Gyam.
Person 3: Yeah, basically.