Probably a single root plant. Crawl under the rosemary and look at how many stems are coming up from the soil.

Short answer - no, it can't be divided.

However, you can remove as many branches as you like, and use them as cuttings to propagate. Cutting can be quite large, but 'take' better if they are not from older wood. From one branch, you might get 20 or more cuttings. Heel cuttings are best.

As a general rule, when pruning any plant, it's best not to remove more than one-third of total growth. But rosemary is quite a determined plant and tolerates pruning better than most - it's an excellent topiary plant - so even with drastic cut-back, it is likely to grow back again.

People forget just how BIG rosemary can get!

I agree that the answer is NO to dividing. I find that the easiest way to get more plants is to gently bend branches to the ground (if not already there) and pin them down; within a month or two the part that's pinned will have rooted, then this can be cut off the parent and transplanted.