2. Verb. (humorous transitive) To render (a thing) compact or more compact. ¹
3. Verb. (mathematics transitive) To enlarge (a topological space) in order to render it compact. ¹
4. Verb. (physics transitive) To adjust a theory so as to render finite or periodic (a theoretical space-time dimension). ¹
¹ Source: wiktionary.com