The Collaborative International Dictionary of English v.0.48:

Moho \Mo"ho\, n. [Native name.] (Zool.)
   A gallinule (Notornis Mantelli) formerly inhabiting New
   Zealand, but now supposed to be extinct. It was incapable of
   flight. See Notornis.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Moho \Mo"ho\, n. [Short for Mohorovicic discontinuity, from
   Andrija Mohorovi[ccaron]i[cacute], a Yugoslavian geologist.]
   (Geol.)
   The boundary between the earth's crust and the semiliquid
   mantle beneath. It varies in depth from 3 miles beneath the
   surface at certain points in the ocean to over 25 miles under
   certain parts of continents.
   [PJC]

WordNet (r) 3.0 (2006):

Moho
    n 1: the boundary between the Earth's crust and the underlying
         mantle; "the Mohorovicic discontinuity averages 5 miles
         down under oceans and 20 miles down under continents" [syn:
         Mohorovicic discontinuity, Moho]