no such word as definital in my dictionary. If itmeant definition, I'm not sure how 'sea of souls' could have one: it was a TV drama, that's about it http://en.wikipedia.org/wiki/Sea_of_Souls
Do you mean definitial? Where you create a sentence with each word beginning with the letters of what's defined (eg. it could start Some Extensive Area Or Flat Space etc etc).
oh yes, of course, it's one of those Radio Times competitions - it includes the word 'initials' so that's how you spell it. And they're usually the names of characters or series. (And you're supposed to do them yourself. But Quizmonkey's given you a start.)