Correct me if I'm wrong, but being offline is not a slashable penalty. You would slowly lose ETH and eventually be ejected, but not slashed like a malicious validator would be.
Maybe I'm applying the term "slashing" too broadly. I've historically used it to describe the act of having your tokens taken away for bad behavior (either all at once, or incrementally). Is there a more-specific term for describing the process by which an offline validator loses their ETH over time?