Vaginismus (the German equivalent of the wor Vaginism) is a condition which affects a woman's ability to engage in any form of vaginal penetration, including sexual penetration, insertion of tampons, and the penetration involved in gynecological examinations. This is the result of a conditioned reflex of the pubococcygeus muscle, which is sometimes referred to as the 'PC muscle'. The reflex causes the muscles in the vagina to tense suddenly, which makes any kind of vaginal penetration -- including sexual penetration -- either painful or impossible.