"sb" is an abbreviation for "somebody".
To ream, generally means to offer sharp criticism of another person.
For example, a common use of the expression would be something like this.
"I reamed that jerk out ....up one side and down the other... for his stupid mistake!"
"I was reamed for giving disrespectful answers to the teach at the school."
"I got reamed out at work by my boss."
"Boy, if you screw this up, I will ream your ass out for sure!"