This resource lists 8 different nuanced meanings: Kosmos Meaning - Greek Lexicon | New Testament (NAS).
This resource lists 3 different meanings, which can be considered distillations of the 8 listed in the previous article; similar meanings are subsumed into one category: World (Kosmos) | Bible.org.
Note especially this:
Dr. Merrill Unger made note of the fact that “In more than thirty important passages the Greek word ‘kosmos’…is employed in the New Testament to portray the whole mass of unregenerate men alienated from God, hostile to Christ, and organized governmentally as a system or federation under Satan (John 7:7; 14:27; I Cor. 1:21; 11:32; 1 Pet. 5:9; I John 3:1, 13; et al.).
If this is the case, then that could very well be the sense in which Peter is using the word, to describe the organized system or order of ungodly men that existed prior to the flood, compared with the world of ungodly men that exists now and at the end times, when that world (and the physical universe, denoted by the Greek word γή) will be burned up (which Peter describes in the next chapter).
@Socratic.Fanatic, you were the one who made the distinction between γή and κόσμος, weren’t you? Perhaps you could shed some light on the subject.