The father of a father is a grandfather, a grandfather's father is a great-grandfather, a great-grandfather's father is a great-great-grandfather, but no word has been decided upon for the generations before great-great-grandfather.
O pai do pai é o avô, o pai do avô é o bisavô, o pai do bisavô é o trisavô, mas não se definiu uma palavra para gerações anteriores ao trisavô.