It is pronounced Gee-ro or Jee-ro - in THIS country. Like many words it has become modified by its use in a non-Greek-speaking county. Both pronounciations are in part a product of dialectical differentiations and of hard 'breathings' contained in the Greek tongue. In certain areas of Greece such as Cyprus and Crete these breathings - which seen to add and deep-throated 'H' sound to many vowels as well as consonants- are more prominant. Furthermore their is no 'Y' in the Greek alphabet. The letter we see as 'Y' in English-used Greek words is the Greek upper case letter 'Upsilon' (not to be confused with the lower case 'Gamma') which looks like an English 'Y' and is pronounced 'oo' as in 'boot'. The Greek letter 'Gamma' on the other hand is pronounced as a hard G like 'gone' or 'gun'. Never - except for in the deceptive breathings and dialectical diferences listed above does there exist any deviation from the pronounciation of these two Greek letters which have been in use for well over 3000 years. The greek word 'Γυρως', spelled in correct Anglo-greek 'Guros' - or 'Gyro' in this country - means circle or - more specifically - rotate: as in how the Lamb's meat of a Gyro rotates on the skewer while cooking. It is a derivitave from Classical Greek and is the root word for the English word 'Gyrate'. So in THIS country you can pronounce it either way; but its correct pronounciation is thus: GOO-ROW or GOO-ROWS. Does that clear any of this up?

Ed/Rochester, NY, fluent Greek-speaker, scholar and traveller; amature Etymologist; and Gyro lover ;)