Questions about example sentences with, and the definition and usage of "Retarded"

A: "Retarded" originally means "slow, regressed". Many have turned it into a harsh insult now, using it towards someone to refer to a mentally handicapped individual. It is not a light insult, and really shouldn't be said. It's extremely disrespectful.

A: Stupid

A: In everyday conversation it is used in the same way as "stupid" or "dumb", to refer to things that someone doesn't like. It's also an insult similar to ばか as mentioned by oahuborn808.

A long time ago the word was used to refer to people who were mentally disabled. It's considered an offensive word now and you shouldn't say it unless you are absolutely sure the person you are saying to won't be offended by it-- but honestly it's best to just not say it at all.