What is the name of this sleeve type?

A question about clothing construction:

I want to make a long, hooded, breathable anorak shell for outdoor winter activity. I’ve been looking for patterns, but I’m stuck on a bit of terminology.
I know that a raglan sleeve has a diagonal seam running from the neckline to the bottom of the armhole. But what do you call the sleeve type where the seam runs horizontally from the bottom of the ‘armhole’, across the chest/back, to the other ‘armhole’?

In other words, the sleeves/shoulders/upper torso are a single piece (or maybe two pieces, with a vertical seam in the middle of the chest/back). I’m thinking that that design would work well to shed snow.

That sounds like a variation on several kinds of “folk” garments that are formed by cutting a single piece which is then folded to create the shoulder/top of sleeve. Cut a neck hole, stitch the sleeve bottoms and side seams and you have a shirt/tunic/dress. I don’t think it has a specific name, though.

It sounds very good for shedding snow and rain, due to the lack of seams on the upper surfaces of the garment.

The closest I could find construction-wise (but not style-wise) is called a Dolman Sleeve. It’s an extension of the bodice pieces, but usually features an extra-deep armhole and tapering at the wrist. If you’re making it yourself, you could of course modify the depth of the armhole. Kimono sleeves are similar and don’t feature the tapering

The problem with this type of construction is that dolman sleeves tend to be somewhat ill-fitting. You may want to consider using a drop-shoulder style instead, as they fit a little bit better, and you could modify it to use one piece for the shoulder/upper bodice piece.

cwPartner reminded me that this is similar to a dolman sleeve (daintycakes beat me to it).

As daintycakes pointed out, the dolman sleeve can be hard to fit - you can end up with unwanted bulk in the underarm. This construction eliminates the shoulder seams while keeping a more typical activewear shape. Sorry, I don’t know what this construction is called - perhaps someone here can identify it?

I would consider that style a modified raglan, but an image search for saddle sleeves gives a similar shirt

Both the dolman and the drop sleeve result in a lot of underarm bulk. Saddle sleeves would eliminate the top seam while making a more comfortable underarm.
There’s a lot of info out there for knitters regarding types of sleeves, their pros and cons, and how to design them. While this doesn’t sound like a knitted project, many of the concepts and measurements still apply (while keeping in mind that woven fabric behaves differently than knitted).