The term comes from #warez. Groups like Razor 1911 and Fairlight would brag about how recent their software was. 0 day was release day. First-run warez.
There are as many different definitions of zeroday in the security scene as there are people with strong opinions, but all the definitions boil down to, "it's zeroday if it's new". There's patched zeroday (when SUNW releases code that fixes a flaw and they don't tell anyone about it, the exploit for that flaw is zeroday). Unpatched flaws are usually by definition zeroday.
It's kind of a silly thing to argue about, since there's no consensus definition. This TLS flaw definitely qualifies by most people's definitions.
There are as many different definitions of zeroday in the security scene as there are people with strong opinions, but all the definitions boil down to, "it's zeroday if it's new". There's patched zeroday (when SUNW releases code that fixes a flaw and they don't tell anyone about it, the exploit for that flaw is zeroday). Unpatched flaws are usually by definition zeroday.
It's kind of a silly thing to argue about, since there's no consensus definition. This TLS flaw definitely qualifies by most people's definitions.