My non-lawyer opinion is that it is what is being supplied as a way for others to describe that page, so there is certainly a good argument that it is implied permission to use the description *to describe that page*.
That is not to say that you have any implied permission to use that description for any other purpose, such as to copy it for use on one of your own pages.
Of course, that does not mean that you are clear of the possibility of being sued. There are certainly plenty of people that will at the very least, threaten legal action even when you are in the right.
I know this most probably sounds a dumb question when you consider that SE spiders swipe them for use in the engines
IANAL but in the UK, meta tags and website product information is covered by database right, so you can't just take it and use it. Search engines don't compete in the same arena - unlike your direct competitor who can take your meta tags.