neologism

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

• noun A new word, expression, or usage.
• noun The creation or use of new words or senses.
• noun The invention of new words regarded as a symptom of certain psychotic disorders, such as schizophrenia.
• noun A word so invented.
• noun Theology A new doctrine or a new interpretation of scripture.

from The Century Dictionary.

• noun A new word or phrase, or a new use of a word.
• noun The use of new words, or of old words in new senses.
• noun A new doctrine.

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

• noun The introduction of new words, or the use of old words in a new sense.
• noun A new word, phrase, or expression.
• noun A new doctrine; specifically, rationalism.

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

• noun linguistics A word or phrase which has recently been coined; a new word or phrase.
• noun linguistics (uncountable) The act or instance of coining, or uttering a new word.
• noun psychiatry The newly coined, meaningless words or phrases of someone with a psychosis, usually schizophrenia.

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

• noun a newly invented word or phrase
• noun the act of inventing a word or phrase