Although the Laws of the Game say a player must be cautioned if he's guilty of unsporting behaviour, a direct definition of what constitutes "unsporting behaviour" is never provided (apart from a very brief and rather generic description given in the Glossary, which merely states that "unsporting behaviour" is any 'Unfair action/behaviour').
Instead, the Laws explain this concept by giving a (non-exhaustive) list of examples, among which this can be found (Law 12.3):
Cautions for unsporting behaviour
There are different circumstances when a player must be cautioned for unsporting behaviour including if a player:
• shows a lack of respect for the game
I've always been curious as to what showing a lack of respect for the game can possibly mean: what's an example of behaviour that can warrant a yellow card for showing a lack of respect for the game that doesn't also belong to any other categories of misconduct? (Including the red card offences as well, so offensive/insulting/abusive actions or words are out of questions since they're already sending-off offences.)