From The Collaborative International Dictionary of English v.0.48 :
Extensively \Ex*ten"sive*ly\, adv. To a great extent; widely; largely; as, a story is extensively circulated. [1913 Webster]From WordNet (r) 3.0 (2006) :
extensively adv 1: in a widespread way; "oxidation ponds are extensively used for sewage treatment in the Midwest"