This question asks about the etymology of the term lingua franca. It can be looked up on Etymonline or Wikipedia with satisfactory result. But this isn't a word definition, and I actually found the top answer interesting to read, though it probably isn't any more informative than Wikipedia or Etymonline.
Should a question like this be closed? From the comments it appears that someone feels quite strongly about it; but, considering that it isn't a plain word-definition question, I'd be inclined to keep it open.