1. (noun) natural family planning in which ovulation is assumed to occur 14 days before the onset of a period (the fertile period would be assumed to extend from day 10 through day 18 of her cycle)

• calendar method
• calendar method of birth control
• rhythm
• rhythm method of birth control

1. (noun) natural family planning in which ovulation is assumed to occur 14 days before the onset of a period (the fertile period would be assumed to extend from day 10 through day 18 of her cycle)

• natural family planning