Pronounced jerr-sh-werr, it is a combination of a jacket, shirt, and sweater. These are normally a tighter fitting garment, and can consist of buttons going either part way down the neck, or the entire torso of the jirshuer. They also normally have hoods, but are not as thick or heavy as a hoodie, instead being made of fabric similar to a regular shirt.
"It's only a little chilly outside. I better put on my jirshuer."
"His jirshuer was fancy. It buttoned all the way up."
"Check out this jirshuer I bought at Pac Sun."