An Etymological Dictionary of Astronomy and Astrophysics

1. Math.: A process applied to topological spaces having many dimensions to make them compact spaces.
   

2. Physics: In string theory, the process of “curling up” the extra dimensions (six in the superstring theory). According to these theories, the Universe actually has 10 spatial dimensions but that 7 of them have become “compactified” down to subatomic size and thus are unobservable.

See also: Compactification, n. from → compactify.