erectile dysfunction

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The inability to achieve penile erection or to maintain an erection until ejaculation. Also called impotence.

Wiktionary

1. n. The inability of a man to obtain or sustain an erection. Abbreviation: ED

WordNet 3.0

1. n. impotence resulting from a man's inability to have or maintain an erection of his penis