Division of guitars by material that are made
If we talk about the wood from which the body (corpus) of the instrument is made, we use the terms massive, semi-solid and plywood.
Solid (all-massive)
If we say that the guitar is a solid, it means that the whole body was made of one piece of wood.
Semi-solid (half-massive)
At least some part of the body (front plate, back plate, ...) was made of one piece of wood.
Plywood
Mostly several layers of wood (or laminate boards) are glued together.