retard is a slur for mentally handicapped people, usually with autism or dyslexia, often used to say someone's stupid or did something stupid. using the word is usually backed up by saying "its the name of a disorder" but the name was changed a long time ago from retard syndrome to cotard syndrome
p1: Jimmy is a fucking retard
p2: stfu he's just stupid
p1: aww poor Tom is retarded
p2: if that your waybof saying he has autism stfu and leave