Meat preaching is weightier and heavier issues that have incredible depth to them, as opposed to milk which is shallow truths basic to Christianity that can be handled by spiritual infants who are newly born again.
1 Corinthians 3:1-2 And
I, brethren, could not speak unto you as unto spiritual, but as unto carnal, even as unto babes in Christ. (2) I have fed you with milk, and not with meat: for hitherto ye were not able to bear it, neither yet now are ye able.
Hebrews 5:12-14 For when for the time ye ought to be teachers, ye have need that one teach you again which be the first principles of the oracles of God; and are become such as have need of milk, and not of strong meat. (13)
For every one that useth milk is unskilful in the word of righteousness: for he is a babe. (14) But strong meat belongeth to them that are of full age, even those who by reason of use have their senses exercised to discern both good and evil.
An example of an issue abthat is considered MEAT is as follows:
Hebrews 9:4-5 Which had the golden censer, and the ark of the covenant overlaid round about with gold, wherein was the golden pot that had manna, and Aaron's rod that budded, and the tables of the covenant; (5) And over it the cherubims of glory shadowing the mercyseat;
of which we cannot now speak particularly.
So sad that the Hebrews were babes, since we could have read what Paul had to say on the cherubims and other ark issues!
Meat is truth that younger believers cannot comprehend.