The Collaborative International Dictionary
Xerophagy \Xe*roph"a*gy\, n. [L. xerophagia, Gr. ?; ? dry + ? to eat.] Among the primitive Christians, the living on a diet of dry food in Lent and on other fasts.
Douglas Harper's Etymology Dictionary
"habit of living on dry food," especially as a form of fasting, 1650s, from xero- + -phagy (see -phagous).
Wiktionary
n. A restrictive diet (of bread and water, for example) as a punishment or religious form of discipline.
Wikipedia
Xerophagy ("dry eating", from Greek "dry" and "eat") is the practice of eating dry food, especially food cooked without oil. In Eastern Christianity, xerophagy is the form of fasting observed during Great Lent and certain other fasts, in which vegetables cooked with water and salt are eaten, together with such things as fruit, nuts, bread and honey.
In some historic and modern military organizations, it may be used as a disciplinary measure.