1. A sex offender is a person who has been criminally charged and convicted of, or has pled guilty to, a sex crime. A crime requiring mandatory sex offender registration can be anywhere from downloading pornographic material of persons under the age of 18 off the internet (child pornography) to rape and even non sexual offenses such as kidnapping, may require registration. The term sexual offender is a broad term, with sexual predator being used to describe a more severe physical or repeat sexual offense. Sexual offenders are also sometimes classified into levels, where the highest level offenders have the most aggravating crimes and thus, the most risk to the public and usually must register as a sex offender for their entire lives. Low level sexual offenders may serve only a probationary sentence and only register for 10 years as well as having less restrictions placed on them compared to higher lever offenders. As a label of identity it is used in criminal psychology. Especially in the United States and the United Kingdom, the person, if convicted, is most likely required to register with the respective jurisdiction's sex offender registry.
2. Somebody who, simply enough, has sex with small children and animals.
1. Did you see on the news that there's a sex offender on the loose in the area?
2. Nate, AKA YourMom in online communities, along with Joshua, AKA Jesta/Jester/Demented Jester in the same online communities, recently declared themselves as SEX OFFENDERs via the vBulletin hack/plugin "Staff Titles".