moron

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A person who is considered foolish or stupid.
• noun A person of mild mental retardation having a mental age of from 7 to 12 years and generally having communication and social skills enabling some degree of academic or vocational education. The term belongs to a classification system no longer in use and is now considered offensive.

from The Century Dictionary.

• noun A variety of salamander.

from the GNU version of the Collaborative International Dictionary of English.

• noun An inferior olive size having a woody pulp and a large clingstone pit, growing in the mountainous and high-valley districts around the city of Moron, in Spain.
• noun (Pedagogy) A mentally retarded person whose intellectual development proceeds normally up to about the eighth year of age and is then arrested so that there is little or no further development; an adult having the mental development of an 8-to-12-year old. A moron is considered capable of doing routine work under supervision.
• noun informal, derogatory Hence, a very stupid person.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun obsolete A person of borderline intelligence in the former classification of mental retardation, having of an intelligence quotient of 50-69.
• noun informal A person who makes uncool, unfunny, uninteresting, or irrelevant (see lame) attempts to impress others and draw attention to himself, especially in a flawed attempt to act like someone else.
• noun slang An idiot.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a city in Argentina, to the west of Buenos Aires
• noun a person of subnormal intelligence