In a tweet she posted during Monday night's presidential debate between Obama and Republican nominee Mitt Romney, Coulter said she highly approved of "Romney's decision to be kind and gentle to the retard."
In an interview with CNN's "Piers Morgan Tonight" Friday, she defended her use of the word "because it's a synonym for 'loser.'"
"Maybe [Vice President Joe] Biden should be upset with me calling the president a retard but not an actually disabled person," Coulter said.
The commentator has faced sharp criticism for her choice of words since her tweet Monday, most notably in a blog post written by Special Olympic athlete John Franklin Stephens, who also appeared Friday on "Piers Morgan Tonight."
"The word retard is offensive, and that I should not be a symbol for someone who is dumb and shallow," he said Friday. "If they wanted to use me as a symbol, use me as a symbol for someone who fights adversity."
Coulter denied the term was offensive.
"It's offensive according to whom? Moron, idiot, cretin, imbecile, these were exactly like retard, once technical terms to describe people with mental disabilities," she said. "Changing the word doesn't change the definition. I was not referring to someone with Down syndrome. I was referring to the president of the United States."