Ormeloxifene (sold under the trade names of Shaleli, Choice-7, Novex-DS, Centchroman and Centron) is one of the Selective Estrogen Receptor Modulators, or SERMs, a class of medication which acts on the human estrogen receptor.
It's best known as a non-steroidal oral contraceptive which is taken once per week. In India, ormeloxifene has been available for birth control since the early 1990s. With current sales in the region of 30 million pills per year. (source Current Science 115(9):1638)
Its precise mechanism of action is unknown, but is believed to be linked to its ability to cause asynchrony in the menstrual cycle.
See: Wikipedia