Yes, you can hide leads that you don't want to see and if you decide you want to un-hide them later that's also easy to do as well. When you hide a lead, all information about the lead and its visits are being deleted. Please bear in mind that hiding leads in bulk is not possible.
You can see here how to hide a company from your lead feed by clicking on Hide company visits.
Here's how to un-hide a company if needed.
NOTE: If you later un-hide a company you will not see previous traffic from that company. Please, also notice that hiding a lead from your feed hides the lead from all of your company's Leadfeeder users.