rhythm method (rith-ĕm) n. a contraceptive method in which sexual intercourse is restricted to the days at the beginning and end of the menstrual cycle when conception is least likely to occur (safe period). The method depends for its reliability on the woman having uniform regular periods and its failure rate is higher than with mechanical methods.

rhythm meth·od • n. a method of avoiding conception by which sexual intercourse is restricted to the times of a woman's menstrual cycle when ovulation is least likely to occur.