Great grandmother and Great grandparent

Great grandmother noun - A mother of your grandparent.

Great grandparent and great grandmother are semantically related. In some cases you can use "Great grandparent" instead a noun phrase "Great grandmother".

Great grandparent noun - A parent of your grandparent.

Great grandmother and great grandparent are semantically related. Sometimes you can replace phrase "Great grandmother" with "Great grandparent", this phrases are similar.