A person made to do hard menial work.
Used as a verb it has connotations of working hard, but not for merit or achievement. Often associated with hard, unrewarding and can be associated with slavery or any form of toil and effort where the rewards are few, to non-existent.
I had to drudge through this book before I could see my favourite characters in the next.
Drudging through the day, I was eager for the clock to strike five.