From The Collaborative International Dictionary of English v.0.48 :
University extension \U`ni*ver"si*ty ex*ten"sion\
The extension of the advantages of university[3] instruction
by means of lectures and classes at various centers.
[Webster 1913 Suppl.]
From WordNet (r) 3.0 (2006) :
university extension
n 1: an educational opportunity provided by colleges and
universities to people who are not enrolled as regular
students [syn: extension, extension service,
university extension]