Today's word is ポシャる. It means for someone's plans to get messed up when they are still half-realized. So lets do a breakdown already!
ポシャ: Comes from シャッポ（chapeau), which is the French word for hat. Also, it is reversed.
～る: A verbalizer (動詞化する接尾語 if you wanna get technical).
The reason why hat was taken from French and then reversed and finally verbalized to come to mean spoiled plans is kind of unclear, but some think it has a relationship to the phrase シャッポを脱ぐ, which is to take of your hat off out of respect.
But anyways, the reversing, or partial reversing of words into slang is pretty common. I remember I did a post way back when I was still green to Japan about まいう (that one was featured on Japundit back then too, because I always had the makings of a Japan blogstar. Oh dear, all this bragging has ポシャらせた my post!) . There are also words like グラサン (reversed from sunglasses) and ワイハー(reversed from Hawaii)
You can find another example or two of a verbalized foreign originating ru-word by visiting a previous slang post I did.
As for usage, it seems to show up most often in past tense, which is not surprising. For example, "運動会は雨でポシャりましたが..."= "The school sports day was ruined by rain".