A cutesy, girlish-sounding word taken from the German game Carcassonne, this word has been adapted to have many meanings, such as "That sucks" or "Oh crap." It can also be a verbal expression of a sigh or puppy-dog face. Whatever the usage, the word is usually expressing sadness or disappointment.
Professor: "The two papers will be due tomorrow. Sorry about the short notice."
Guy: "I'm working through some serious health issues right now."
Girl: "Meeple... I hope things go okay."