One of the functions most missing in Urbandictionary.com

word meaning similar to another word

1. A word that means the same, or almost the same, as another word in the same language, either in all of its uses or in a specific context.

2. a word or expression that is used as another name for something in some styles of speaking or writing or to emphasize a specific aspect or association.

3. A duplicate taxonomic name that has been rejected or replaced.

A word you use when you don't know how to spell the first one.

<noun>

A word that has the same meaning as another.

George W. Bush's favorite flavor.

Different words, but have the same definition.