What is meant by "The son of Adam denied Me and insulted Me"?

The denial here is the disbelievers' rejection of Allah's ability to resurrect them after their death. As for the insult, it refers to the disbelievers' ascribing a son to Allah the Exalted. Allah Almighty said: "My servant denied Me, and he had no right to deny Me. And My servant insulted Me, and he had no right to insult Me. As for his denying Me, it is his saying: 'He will not restore me as He created me the first time.' And the first creation is not easier for Me than its re-creation. As for his insulting Me, it is his saying: 'Allah has taken a son.' And I am Allah, the One, the Self-Sufficient. I did not beget, nor was I begotten, and there is none comparable to Him."