To be soundly beaten; pwned/owned; utterly defeated; beaten severely
The term comes from the idea of gingers (people with red hair and fair skin) being inferior and/or worthless. See also: beaten like a red haired stepchild - this ginger version may be more commonly used in the UK.
"I've never played this game before; I'm going to get beaten like a ginger stepchild by her."
"If I come home late again, my dad is going to beat me like a ginger stepchild."