Verb
(humorous, intransitive) To become compact or more compact.
(humorous, transitive) To render (a thing) compact or more compact.
(mathematics, transitive) To enlarge (a topological space) in order to render it compact.
(physics, transitive) To adjust a theory so as to render finite or periodic (a theoretical space-time dimension).
Source: en.wiktionary.orgAfter Calabi–Yau manifolds had entered physics as a way to compactify extra dimensions in string theory, many physicists began studying these manifolds. Source: Internet
One did not have to explicitly impose a cylinder condition, or to compactify: by assumption, the gauge group is already compact. Source: Internet
This is harder to compactify. Source: Internet