Morning-after pill: A form of contraception used after rather than before sexual intercourse. Morning-after pills interfere with pregnancy by blocking the implantation of the fertilized egg in the uterus (womb). The pills contain the same drugs as regular birth control pills, but in higher doses, and work the same way. Morning-after pill is a misnomer because these pills may be taken up to 3 days after unprotected sex. The term was coined back in 1966. Also known as emergency birth control pill or EBC pill. See also: Emergency contraception.