A pagan, heathen, infidel, or non-believer was an individual who held certain ancient religious beliefs outside of the mainstream.
After the USS Enterprise was attacked in a "cold-blooded" Romulan ambush in 2269, the agitated Montgomery Scott wished to "give the heathens a fight they won't soon forget." Captain James T. Kirk however disagreed, because they were outnumbered, three to one. (TAS: "The Practical Joker")
According to Sybok, as of 2287, modern dogma incorrectly considered Sha Ka Ree a myth concocted by Pagans. (Star Trek V: The Final Frontier)
The Rumarie was an ancient Pagan festival, that as of the late 24th century had not been observed for a millennium. (VOY: "Meld")
During a sermon given by The Doctor in the Paris 042 Fair Haven holoprogram, he told a story of two neighboring farmers, one of whom took revenge on the other for refusing to replace the plow that he had broken, took it upon himself to clog the irrigation ditch of the first farmer. The Doctor went on to ask, "Now, do you think their disagreement stopped there? Of course not. They go on, just as the heathen did of old. After all, one spiteful act deserves another, right? Wrong! What these sinners have forgotten is that they are neighbors." (VOY: "Fair Haven")