Question:
What does transgress or transgression mean?

Answer:
“Where no law is, there is no transgression” (Romans 4:15). An example of this is when a line is drawn and a law is set not to cross the line. If you cross it, you transgress. So transgression is a violation of a commandment.

Was there any sin between the times of Adam and Moses? Yes, but the law was not given until Moses, so men were not transgressors (Romans 5:12-14). Noah lived between Adam and Moses, and there was sin in Noah’s day, and it was because of man’s wickedness that the flood came (Genesis 6:5-7).
Sin is lawlessness, rebellion, doing my own will (1 John 3:4). Transgression is going against a specific commandment, and knowing it—something that you are aware is wrong (1 John 2:3-6).