the period during the menstrual cycle when conception is considered least likely to occur
See also rhythm method
safe period in American English
noun
an interval of the menstrual cycle when fertilization is considered to be least likely, usually a number of days prior and subsequent to the onset of menstruation
Word origin
[1915–20]This word is first recorded in the period 1915–20. Other words that entered Englishat around the same time include: collage, decoder, soviet, stockpile, takeout