Glossary
What do VFR, MVFR, IFR and LIFR mean?
A shorthand for how good or bad conditions are, worked out from the reported ceiling and visibility together. VFR is the best of the four and LIFR the worst, with MVFR meaning marginal. The categories are a briefing aid; the legal minimums for a flight come from the regulations for the airspace being flown in.
Also called MVFR, LIFR
That is the whole entry for now. The longer version, with the mechanics and worked examples, is still to be written. See autorotation for how those read once they exist.