1. An unintentional snark that gets noticed by someone.
2. Unintentional sarcasm. (see Clueless Asshole)
3. A snark that escaped before you could stop it. (see Burp)
"Oops, sorry about that snurk. I didn't mean for it to come out that way."
"I just claimed snurk on that one. What can I say? My bad."