From The Collaborative International Dictionary of English v.0.48:

MDMA MDMA n. Methylenedioxymethamphetamine, a drug designed to have the effects of amphetamines but originally synthesized to avoid the drug laws; it is now a controlled substance. It is informally called ecstasy. It is used by some abusively and illegally without a prescription. [acronym] Syn: methylenedioxymethamphetamine, Adam, ecstasy. [WordNet 1.5 +PJC]

From The Collaborative International Dictionary of English v.0.48:

methylenedioxymethamphetamine methylenedioxymethamphetamine n. a drug designed to have the effects of amphetamines but to avoid the drug laws, but now a controlled substance. Called also MDMA. Syn: MDMA, Adam, ecstasy. [WordNet 1.5]

From WordNet (r) 2.0:

MDMA n : a stimulant drug that is chemically related to mescaline and amphetamine and is used illicitly for its euphoric and hallucinogenic effects; it was formerly used in psychotherapy but in 1985 it was declared illegal in the United States; "MDMA is often used at parties because it enables party-goers to remain active for long periods of time" [syn: methylenedioxymethamphetamine]