What is a "white martyr"?

Has anyone knowledge of this term?

It is a martyrdom in which there is no violent death. The traditional “red martyrdom” is when a Christian is killed for his faith. “White martyrdom” is when a Christian totally commits his life to God, uniting himself completely to God. Often “white martyrdom” involves tremendous suffering accepted and offered up to God in union with the cross of Christ. To date, “white martyrdom” is a pious classification of the sufferings of certain saints and not an official category of martyrdom in the Church. Examples of those who might be said to have endured a “white martyrdom” include St. Therese of Lisieux, St. Gianna Beretta Molla, and Pope John Paul II.

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