1. Literally, to say "goodbye" to someone when parting. Say goodbye to your mother before you leave!

2. To lose or end something, especially suddenly; to be forced to accept such a loss or end. You were caught drinking on school property? Well, you can say goodbye to your brand new car, mister! After the final horse lost its race, I said goodbye to all the money I'd won that day at the track. You do realize that you'll be saying goodbye to all the benefits the company has to offer if you decide to work as a freelancer?