meg·a·lop·o·lis 
(mĕg′ə-lŏpə-lĭs)
(mĕg′ə-lŏpə-lĭs)n.
1. A very large city.
2. A region made up of several large cities and their surrounding areas in sufficient proximity to be considered a single urban complex.
[MEGALO- + Greek polis, city; see pelə-3 in the Appendix of Indo-European roots.]
meg′a·lop·o·listic adj.
meg′a·lo·poli·tan (-lō-pŏlĭ-tən) adj.