Hi,
I don't think that the Smart Search component in Joomla has the capability to dismiss some of the indexed content.
From what I can read, it would require not indexing the content in the first place:
forum.joomla.org/viewtopic.php?t=1000353
For HikaShop's product description, you can edit the file plugins/finder/hikashop/hikashop_j4.php (or hikashop_j5.php for someone on J5), and then change the line:
return Helper::prepareContent($summary, $params);
to:
Then, reindex the whole content and it should do it.
Note however that you will loose this change each time you update HikaShop.
To have a permanent solution, you would have to develop a copy of the finder hikashop plugin as suggested on that forum post, but it's a lot of work compared to just changing one line of code after updates...