Come learn 2000+ kanji and 6000+ vocabulary words with WaniKani.
Large, Drastic, Substantial, Major
noun, な adjective
Something big in width is still big, in fact it's of a pretty substantial size.
The readings for this word are both kun'yomi readings. You've learned both of these readings by now so you should be able to read this on your own.
The meeting’s documents were largely changed.