A holomorphic Lagrangian fibration is a proper surjective holomorphic map 
with connected fibers from a holomorphic symplectic
manifold of complex dimension 
to a normal complex space of dimension 
, such that every irreducible component
of every fiber has dimension 
and the symplectic form
vanishes on its smooth locus. Smooth fibers are complex
Lagrangian submanifolds.
Projectivity of the map means the existence of a relatively ample holomorphic line bundle. Together with projectivity
of the base it makes 
projective.
