I would be hard pressed to think of a term that is less familiar to us in the North American context. But it is potentially relevant to this topic, and should at least be laid out beside the other possible arrangements for parishes and the structural provision of pastoral care. The second half of c. 374 reads:
§2. To foster pastoral care through common action, several neighboring parishes can be joined into special groups, such as vicariates forane.
From the standard commentaries on this canon, the reader can learn that vicariates forane are also called deaneries, but little else is said. But at least we know the word deanery, so we know what we are talking about now. It is also evident from the text of the canon that, while the division of each diocese into territorial parishes is required by the law, the supra-parochial division of the same diocese into larger groupings is completely optional. But it is possible that this notion, when it is applied in dioceses, is extremely underused.
In the 1973 Directory on the Pastoral Ministry of Bishops we can read:
The supra-parochial office of the vicar forane has a pastoral character, that is, not only juridical and administrative; it also has an important function. In effect, the vicar does not only have the obligation of vigilance, but also that of a true apostolic solicitude, as one who encourages the life of the local priest and one who coordinates the pastoral organization at the forane level….
At the end of his case study of the diocese of Brugge and their sweeping application of c. 517, §1 establishing priests acting in solidum, Kurt Martens wonders whether essentially the same cooperative pastoral arrangement would not have been a better, simpler fit under c. 374, §2.
Indeed, that canon offers the possibility of clustering neighboring parishes into special groups and gives the vicariates forane as an example. The advantage of canon 374, §2 is that these structures can be set up somewhat freely, possibly with the deans as the key figures in such configurations, although that is not required, while the solution of canon 517, §1 requires at least that the pastoral care of one or more parishes is entrusted in solidum to a group of priests while one of them is appointed the moderator. Canon 374, §2 offers the particular legislator ample opportunities and also keeps the existing parishes intact….
The legislation specifying the scope of duties of the vicar forane, or dean, if you prefer, (cc. 553-555), seem to indicate that it is a very flexible institution which a diocesan bishop could easily customize through particular legislation to achieve the right solution for a great many pastoral challenges. If desired, the same customizable structure could be established as an Episcopal vicariate, with the vicars in each given the power of a local ordinary within the scope of their vicariate. This last is not a solution that would be called for in a small diocese, perhaps, but certainly one with possibilities worthy of reflection.
 Sacred Congregation for Bishops, Directory on the Pastoral Ministry of Bishops, Ecclesiae imago, 22 February 1973, as quoted in ExComm, Vol. II/2, p. 1395.
 Kurt Martens, “The Parish Between Tradition and Renewal: Theoretical Consideration and a Case Study of C. 517, §1,” in The Jurist, 69 (2009), p. 369.
 See c. 476 and following.