Less-active Mormon

Less active and inactive are terms historically used by members of The Church of Jesus Christ of Latter-day Saints (LDS Church) to describe a person who is not actively participating in the church, but who is still on church membership records. Generally speaking, these are individuals who do not attend church services and are not otherwise involved in church activities or callings. Some less-active members maintain good relations with and positive feelings toward the LDS Church. Reasons for disengagement can include lifestyle issues and problems with social integration.
The LDS Church does not release statistics on church activity, but it is likely that about 60 percent of its members in the United States and 70 percent worldwide are less active or inactive. Activity rates vary with age, and disengagement occurs most frequently between age 16 and 25. Young single adults are also more likely to become inactive than their married counterparts, and overall, women tend to be more active than men. A 1998 study showed that a majority of less-active members return to church activity later in life. Further research has shown that "a completed mission correlates well with staying Mormon for the long term, even among people who were not very active in the LDS Church growing up. In other words, eight in ten people who had been less active as kids were still Mormon in adulthood if they had served a full-term mission." 
The Jewish equivalent of "less active" is "non-observant." The Catholic equivalent is "non-practicing" or "lapsed".