Noob biologist here. I suspect that at the first stage this means 'activating the virus by lysis of a surface/spike protein'? Seems kind of obvious, but I put it here in case 'proteolytic activation' is not in fact merely a subset of 'virus activation', and means something slightly different.
Second, if the above interpretation is correct, what precisely do we mean by virus activation? Is it the release of viral RNA into the host cell cytosol? This would be my guess, as it is necessary (sufficient?) for replication of viral RNA to commence, and viral replication to occur. Another idea is that 'virus entering host cell' is enough to constitute viral activation, though I suspect some viruses can enter cells and remain dormant there. Hardly seems like activation to me.
Would really appreciate clarification of this terminology so I don't have misconceptions when reading literature.