tear-eye-ah is how i've always thought of it

(tear as in rip, not crying)

I'd say tear-ee-ah.

I'd say tear-ee-ah.

That's how I say it

[JuZ]

That's how Dev said it when he and SYL toured it in Australia, so it works for me!

I'd say something like ter-yah or te-ree-ah (depending on how much you accentuate the middle sonud^^), with the te/ter as in terror (as said upon), as it seems to be based on Terra in Latin (or Terre in French, but this one comes straight from Latin) (in French such a word should be said in 2 syllables, in English the "r" are not as strong as in French so the accentuation may be on the "i" and sound like 3 syllables).
(I'm just being picky^^)

Anyway you can here him say it 3 times himself on the comments of the limited edition of Terria, accentuating the middle sound more or less :
http://overhighwill.free.fr/Terria.mp3

I've always said it "Tuh-rye-ah"... occasionally "tear-rye-ah". But generally the first one. Just seemed to come naturally when looking at it.