Look at the CR and see if those terms are bolded and if the CR states that bolded items are as defined in the ERS (equipment rules of sailing).

If so, Personal Equipment is defined in ERS C5. 

From the Equipment Rules of Sailing:

C.5.2 Personal Equipment
All personal effects carried or worn and items worn on board to keep warm and/or dry, and/or to protect the body, personal flotation device, safety harnesses and hiking aids worn to keep the person aboard or afloat.

I would suggest a watch is a personal effect so, is covered under this.

it is bolded, but it's a section heading, which all are bolded.

E.g. 49er

I would view it as portable equipment, especially as these days it may have additional electronic facilities - such as GPS and compass - and might run afoul of the requirements of any portable equipment restrictions.

I think most class rules were written before watches had much of the tech that a portable sailing computer had. I imagine most classes haven't updated because it's not been raised.

There is also a practical limit to what can be done with a watch in a dinghy, so perhaps it's seen as self limiting and can be left as a free for all?

But I would like to know if there is a solid definition and it seems there is. 

I would think the term "watch" is too generic these days.  If it is purely a timepiece, probably personal equipment.  But if it is GPS, or smartwatch with sailing apps loaded, could be portable equipment.  It's a good example of a term that doesn't have relevance in today's tech world.  Just my thought.

although it is definitely wearable tech and the definition above says 'worn'. 

Maybe it's just something that will have to become a issue before it is addressed my updates to class rules.

Many dinghy classes define what electronic aids can and can't be used - e.g. RS800 allows digital compass, but not GPS.  Interestingly. it's written to allow devices that show only the boat's heading - it's less clear that, for example, whether a historical graph of heading could be used.  It may only show (a history of) heading information, but if the boat is close-hauled, it can help understand oscillation frequency of a breeze.....

I was actually involved with the re-write of the 800 rules. 

The old rules just said 'means of recording information' were permitted. But we wanted to make it clear that camera's were allowed but limit the mounts so as not be overly obstructive. 

We also discussed how gps is a 'means recording information' and most action camera's record GPS. So GPS recording is allowed. We wanted to limit people 'sailing by the numbers' with fancy GPS boat mounted computers... so you can't display speed or position (but can record). Plus the existing limits on compasses limit that particular device to heading and elapsed time.    

But, all that is regarding portable equipment, not personal equipment. We were aware people could be use smart watches, but as it hadn't been an issue to date we didn't change the personal equipment rules. 

But I would say it is a grey area and if you ask most sailors with similar class rules they would say GPS watches are not allowed. But whether that's a considered view, or based on historical limits on mounted race computers.