I dare you to try. If you can give a complete definition, I’ll give you a gold star. Even John Paul II struggled with this definition: “What is meant today by “movement”? The term is often used to refer to realities that differ among themselves, sometimes even by reason of their canonical structure.”
Some might define a lay ecclesial movement in the Catholic Church by pointing to examples: Regnum Christi, Opus Dei, Neocatechumenal Way, Cursillo, Focolare, etc. Or they might point to the Directory of International Associations of the Faithful as a list of the big ones. Here’s a problem: of the 5 examples I listed at least 1 and maybe 2 aren’t movements: Opus Dei is a personal prelature not a movement, and the Neocatechumenal way argues that they are not a movement. They state: “According to its statutes, the Neocatechumenal Way is not a movement or an association, but an itinerary of Catholic formation.”
However, there has been a decent amount of talk about movements and we need some working definition to begin with. We can’t talk about how movements involve young people in the Church, evangelize, or lead people in discipleship if we don’t know what they are.
Instead of beginning with a definition, let’s go through some characteristics and end with a definition based upon them all:
First, lay movements fall in the canonical category of associations of the faithful. Even if they involve other canonical structures like religious communities, the overall structure is an association.
- Second, they primarily involve lay people (not excluding religious or priests but having them in a minority). Some groups, such as the Sisters of Mary, Mother of the Church start as associations with all the other characteristics but have the formation of a religious community as the goal.
- Third, theyare united around some particularcharism, a particular way of life
- As a consequence of this, they each ask members some part of Christian life beyond the precepts of the Church.
- Fourth, they build up the Church. What they do helps the whole Church not just seeking their private good like a prayer group.
- Fifth, they are independent of diocesan and parish structure. They work within it but do not depend upon it. “Before [Pentecost 1998] they were the misfits of the Church. They weren’t religious orders. They weren’t parish organizations. They were lay-driven groups who helped in their parishes while also looking to leadership outside the diocese for direction and inspiration.”
- Sixth, from the previous 5, they develop some new form of communion. “The newness that the ecclesial movements contribute to the Church is not so much new forms of mission or new forms of spirituality but new forms of communion.”
- Finally there is a criterion I would not include but seems to be the criterion the Neocatechumenal way uses to say they aren’t a movement: self-identification. This means something can only be a movement if it says it’s a movement.
Neither the Vatican nor the USCCB has attempted a definition as far as I know. When searching for a definition for Wikipedia, the only official definition I found was from the CEI (Italian Bishops’ Conference) in 1993. The CEI says the following is applied loosely: “The name ‘movement’ is attributed to those aggregate realities in which the uniting element is not primarily institutional structure but a ‘vital’ adhesion to some strong ideas and a common spirit.” I find that helpful but incomplete.
So given all that discussion, the closest thing I can find to a complete definition is: A lay ecclesial movement is an association of the faithful involving primarily lay people in a new form of communion around a particular charism to build up the Church asking certain commitments of Christian life from its members while separate from diocesan and parish structures.
(Note: this is based on part of a paper I wrote for my STL; when the paper got to long this discussion was radically shortened. That is why it has footnotes.)
 John Paul II, Message for the World Congress of Ecclesial Movements and New Communities, May 27, 1998, #4, http://w2.vatican.va/content/john-paul-ii/en/speeches/1998/may/documents/hf_jp-ii_spe_19980527_movimenti.html.
 Junno Arocho Esteves, “Renewal in the Spirit, Neocatechumenal Way Leaders Meet with Pope” in ZENIT, Rome, December 05, 2014, http://www.zenit.org/en/articles/renewal-in-the-spirit-neocatechumenal-way-leaders-meet-with-pope.
 Tom Hoopes, “Groundswell: The Pope, the New Movements, and the Church” in Catholic Cuture, https://www.catholicculture.org/culture/library/view.cfm?recnum=6524.
 Owen Kearns LC and Patrick Langan LC, The Quest for the Core: of the Regnum Christi Charism, (CreateSpace, 2014) Kindle edition.
 “Le aggregazioni laicali nella Chiesa: nota pastorale della commissione episcopale per il laicato” in Notiziario della Conferenza Episcopale Italiana, Num. 4 April 29, 1993, page 88, http://www.chiesacattolica.it/cci_new/documenti_cei/2012-10/12-1047/Le.aggregazioni.laicali.nella.Chiesa.pdf. (Note: personal translation).