Definition of previewing:
(n) :
(colloquial) An advance showing of a film, exhibition etc.
(n) :
A short collection of clips edited together to advertise a film, television show, etc.; a trailer.
(n) :
An experience of something in advance.
(n) :
Something seen in advance.
(n) :
(computing) A facility for viewing and checking a document or photo, or changes to it, before saving or printing it.
(v) :
(transitive) To show or watch something, or part of it, before it is complete.