These are books that were written in the mid 1970s through the early 1990s. The novels are usually over 400 pages long and are sometimes divided into ‘book 1′, ‘book 2′ and usually ‘book 3.’ The stories span many years, usually more than five, take place in several countries (usually America, England, Scotland and Ireland) and often times the hero and heroine are separated for a large part of the novel. The heroine usually suffers from some sort of physical abuse and/or rape by the hero and/or other men. Often times both hero and heroine cheat on each other.
Having said all that, obviously not all of that goes on in every bodice ripper and not all heroine's are raped by anyone.
If you need some idea of what a bodice ripper is, check out my reviews for the books Jemma, Stormfire, Tender Torment, and Into Passion's Dawn.
This is my personal opinion of what bodice rippers are and these statements are in my own words, not stolen from someone else. I've been stolen from before.