Functional Show Stopper comes as one parameter of 'Priority'. I know Show Stopper.. but what is Functional Show Stopper ? What kind of issues can be categorized under this ?
This sounds like, to me, simply a "shop term", something someone came up with in a particular location or locale. A quick Google search didn't really find much of anything to categorize this term or define it in a global way.
So, a "show stopper", as I understand it, is a bug that makes the software product and/or feature being released critically unstable to the point that releasing it would cause the application and/or feature to be just a load of useless bits sitting on the hard drive. So, a "functional show stopper", while it might not totally trash the application, would mean that the bug gets in the way of the intended functionality in such a way that a particular function or feature does not meet requirements and is even un-usable in it's current state. It might not completely destabilize the application but it essentially will mean that the designated feature of the application might as well not be there.
I'd agree with Tristaan that "functional show stopper" sounds like a term that your organization uses for internal tracking purposes.
I'd suggest you start by asking people you're working with for a clarification of how you're expected to use the term. It could mean anything from "this function is unusable" to "this is a show-stopper bug that is triggered by a function" (compared to a "performance show-stopper" like "it takes half an hour to load the application and data entry is accepted at a rate of one character every two seconds") (Don't laugh - I've had to work with applications like that...)
According to Wikipedia the definition of Showstopper:
A hardware or software bug of extreme severity which requires an immediate fix
What's a "Functional Show Stopper"?
Maybe a broken module which needs an immediate fix.
Where do you see this term? You wrote "Functional Show Stopper comes as one parameter of 'Priority'." Sorry, I don't understand this sentence.
I heard about this term 4 years back from now in one of the Trials defects triage call. Show Stopper/Functional Show Stopper is used to categorise defects which makes the entire system unusable i.e. there is no workaround and must be fixed before Live deployment. E.g. Defect Summary: Set top box does not respond at all and a black screen is displayed post software upgrade.
Impact: Users are unable to use any feature. Reboot does not resolve the issue. Code downgrade is not supported, hence only way to resolve this issue is to replace the affected box with a new one.
As mentioned is the above example, there is no way post code upgrade to recover the same Set top box.
My understanding of the common use of functional show stopper is that is about an issue that affects a key piece of end user functionality and is visible to end users.
For that reason alone it is a show-stopper on the release.