Definition of jack mormon
1
: a non-Mormon living in a Mormon community and sympathetic to or on friendly terms with his neighbors
2
: a Mormon inactive in the church or not adhering strictly to Mormon tenets : a backsliding or nominal Mormon
always paid his tithes—only he had to have his coffee so some called him a jack Mormon — American Guide Series: Arizona a jack Mormon, which means that … he no longer pays tithes or holds with the tenet of total abstinence— A. J. Liebling