I believe he means Laminate.. like Formica (like Frogger woodgrain sides) or Melamine (like Nintendo Cabinets).
I have an original (low 300 serial number) Galaga cabinet still with sideart. It is basically painted plywood, just like PacMan and Ms.Pacman.
It has all plywood sides and front, top and bottom fixed back pieces; but the top piece, removable back and inset around the speaker/monitor are particle borad.