Which word refers to someone who is deeply religious?

The term "devout" refers to someone who is deeply religious or devoted to their faith. This word conveys a sense of sincere commitment and reverence, often associated with a person who actively practices their beliefs and maintains a strong spiritual life. It implies not just a surface level of faith but a profound dedication to religious observance and principles.

In contrast, the other options do not bear this meaning. "Ballest" refers to a material used in construction or to stabilize, far removed from religious connotations. "Rancour" denotes bitterness or resentment, typically towards someone else, which is unrelated to religious devotion. "Rampant" describes something that is flourishing or spreading unchecked, again lacking any connection to the idea of deep religious faith or practice.