"Missionary activity" refers to the work or efforts carried out by individuals or groups who spread and teach a particular religion or belief system to people who may not follow or be aware of it. Full definition
Oddly enough, the church was not the center of missionary activity in the early 20th Century: Rather, the individual mission was, as directed by the missionary sending agencies. (christianitytoday.com)
If strictly enforced, the laws could «stop missionary activity to anybody but representatives, registered organizations, and groups,» he said. (christianitytoday.com)
We believe that there's a time for missionary activity and there is a time when it is no longer appropriate. (religion-online.org)