1. a person who journeys, especially a long distance, to some sacred place as an act of religious devotion: pilgrims to the Holy Land.
But our author seems to be using the fifth meaning.
5. a newcomer to a region or place.
Here's what the book says (on page 216):
"Becoming a pilgrim means becoming a local, a year-round person, who adopts a new place and a new identity by learning a new language, rhythms, and practices. Unlike being a tourist, we embark on a pilgrimage, not to escape life, but to embrace it more deeply, to be transformed wholly as a person with new ways of being in community and new hopes for the world. Being a tourist means experiencing something new; being a pilgrim means becoming someone new. Pilgrimages go somewhere to a transformed life."