Erectile dysfunction: A consistent inability to sustain an erection sufficient for sexual intercourse. Commonly known as impotence. Medically, the term erectile dysfunction is used to properly differentiate this form of impotence from other problems that interfere with sexual intercourse, such as disease, injury, drug side effects, or a disorder that impairs the nerve supply or the blood flow to the penis. Other forms of impotence include lack of sexual desire and problems with ejaculation and orgasm. Erectile dysfunction is treatable in all age groups, and treatment includes using medication (notably Viagra) and penile implants. Abbreviated ED.