YOU BET!
Using the Bulk editor. Select your listings and then go to Item Description and then add to Item description.
Bulk edit from Seller Hub
Go to Item Description
Select from your dropdown menu
My only word of caution is that if you add a bunch of fancy boldface or colour to the item text you're adding, you won't be able to bulk remove it the same way you added it. The software can spot plain text for auto-removal but once you add html; to it, no dice. It's stuck there until you take it out, one at a time. I learned this the hard way. Twice. On over 500 listings at a time. It was painful. It's supposed to work seamlessly (the auto-removal) but it just doesn't.