Gedday means, "Hello, how are you?", in the friendliest of manners, this is said by many Australians to each other, as well as to strangers.
Literally it means "Good Day", a common Australian informal greeting.
*also Gedday may be spelt in various ways, such as- G day - g'day - gidday and ged day.
Alvin, "Hey Man Yeh, good, hey!"
Wesley, "Sweet, good to hear."