What is the meaning of Carry-on?

Taken onto an airplane (or a ferry, etc.) with a passenger, rather than checked.

That luggage or baggage which is taken onto an airplane (or a ferry, etc.) with a passenger, rather than checked.

A bag, suitcase, etc., used to carry this luggage or baggage.

A palaver; a disorderly or absurd situation.

Source: wiktionary.org