I'd assume he means the position on your forward between your eyes and up about an inch or two. Some people feel as though that area in particular is pulsating when they trip.
If your on 3 or more hits of acid you don't even need your normal eyes. Your third eye is seein a whole other world!
I always feel a vibration there when on acid, but im starting to think that it is actually my eyes vibrating, and that they have infact rolled into the back of my head, making it feel as though its coming from my forehead... I start that vibration and then i slip accross... weird hey... Feels very similar to mdma 'eye wobbles' if u've had strong M... but in your forehead.
The Third Eye is a western reference to what is also known as AJNA, a Chakra located at the bindu(bindu is the dot hindus wear on their foreheads) between the eyes and up slightly. The third eye is where the whole body's nerves system is connected, it is the largest nerve bundle in our bodies. Stimulating this nerve center and "looking" through AJNA is the way to GOD. See and realize GOD. This chakra is responsive to the pineal gland which lies in the very center of the brain. This is not "eye wobbles".