Hollow body vs. "Semi-Hollow"... ?

Can someone please explain the difference, with examples? My friend has an Epi Sheraton and insists that it`s considered a "semi-hollow body"... seems pretty damn hollow to me. WTF??

Semi hollow bodies have a block running through the center of the guitar to help reduce feedback and improve sustain.

guitar. The sides/wings are hollow.
A the top of a true hollow-body would be held rigid by bracing, like an acoustic guitar.
Some guitars have a block only under the bridge, in order to support it better. These guitars could probably be marketed as either semi- or fullly-hollow.
I *think* the Sheraton II is semi-hollow, and the Casino is bridge-only blocked. Not sure though, and Epiphone`s web site doesn`t make it clear.

Hollow body guitars, like the Epiphone Casino are exactly what the name implies - hollow. The only things inside the cavity are wires and air.
Semi-hollow body guitars, like the Gibson ES-335 have a solid tone-block of wood inside the hollow cavity, generally under the pickups. This block of wood has several effects. First, it makes the guitar much heavier. This can result in better sustain and more back pain. Another effect is that microphonic feedback is reduced compared to a hollow guitar as the air inside has less room to vibrate causing the howl.
I don`t know about the Sheraton in particular, but if you look inside, you can actually see the wood block if it is semi-hollow. Another sure fire test is to just heft the axe. if it feels hollow, it is. If its weight is similar to a Les Paul, its semi-hollow.

I have a Les Paul Signature (semi hollow body) and it`s much lighter than any solid body I`ve owned, including my strat.