One who appears to be as stupid as a mentally retarded person, but not because of lack of intelligence but just because they're foolish.
"Henry, for the last time stop playing Russian Roulete like a total fooltard
A person whos personal actions represent them as foolish and retarded at the same time.
Can also be used as an adjective
The silly fooltard Joe met his demise when he had sex with his fooltarded girlfriend Denise.