What are Meso compounds?

A meso compound is an achiral compound that contains two or more chiral centers. It is superimposable on its mirror image because it possesses an internal plane of symmetry, making it optically inactive.

The definition of a meso compound is:
A meso compound is an achiral molecule that has multiple chiral centers but is optically inactive due to an internal plane of symmetry or a center of inversion.

$\boxed{\text{Meso compounds are achiral molecules with chiral centers that are optically inactive due to an internal plane of symmetry.}}$