What is a slasher film?

Is there a general consensus on the definition of a slasher film. Is that definition varied by era (e.g., 80s vs 90s vs 2000)? There was a recent post in regards to You're Next being a great modern slasher and while I love You're Next (my fav movie that year), I never really considered it a slasher but more of a inverted home invasion/survival horror movie.