Well, depending upon context, I think it just means "more." If a lady offers an FBSM+, she is giving you something additional, like a happy ending, but putting in the symbol is a shortcut, and arguably less legally or morally offensive. If she's 40+, it means she's over age 40 but not yet 50 (and might not want you to know that she's 49), or a reviewer may not know her exact age. A gentlemen might not remember the exact chain of events or want to go into great detail if he's describing session activities so just adds the "+." I believe "++" just means LOTS of extras, like activities or time.