There is, unfortunately, no universally accepted legal or theological definition of the word.

As a working legal definition, The Voice of the Martyrs in Canada has found it helpful to understand persecution to be a situation where Christians are repetitively, persistently and systematically inflicted with grave or serious suffering or harm and deprived of (or significantly threatened with deprival of) their basic human rights because of a difference that comes from being a Christian that the persecutor will not tolerate. When faced with situations where is difficult to determine whether this is a situation of persecution or general suffering, it is helpful to ask, "If a person had other religious beliefs or would change their religion to the majority religion of the country, would things get better for them?" If the answer is "yes," then it seems that this would be a situation where persecution is taking place.

A theological definition is no easier to come by. However, a definition that is consistent with scripture would be: Persecution is any unjust action by authorities, individuals, or crowds of varying levels of hostility perpetrated primarily on the basis of religion and directed at Christians, resulting in varying levels of harm (ranging from ridicule, restriction, certain kinds of harassment, or discrimination to torture, imprisonment, ostracism, murder, and execution) as it is considered from the victim’s perspective.

The Greek and Hebrew words often translated as "persecute" carry a sense of serious violence, aggression and hostility or the threat of such. There is an intent to injure and is carried out in a hostile, antagonistic spirit. In such passages as Jer.29:18 and Ps. 71:11-13 to “persecute” carries with it the idea of "to follow after or pursue." The Greek word dioko and its derivatives used in the New Testament (e.g. Matt. 5:12; Acts 22:4; 1 Thess. 2:15) has virtually the identical meaning of "pursuing or driving away." The term thilipis, means to "oppress or afflict" (Matt. 24: 9; Acts 3:14; 2 Cor. 1:5; 4:10).