The Collaborative International Dictionary
Con- \Con-\ A prefix, fr. L. cum, signifying with, together, etc. See Com-.
Douglas Harper's Etymology Dictionary
Etymology 1 pre. 1 (context non-productive English) used with certain words to add a notion similar to those conveyed by with, together, or joint 2 (context non-productive English) used with certain words to intensify their meaning Etymology 2
pre. 1 attached to certain words to obtain new, informal, subcultural words in which '''con-''' conveys a notion of: 2 # constructed, artificial 3 # hypothetical, fictional 4 # related to conlangs, conworlds, etc.