Half-deaf would be a very casual way to refer to partial hearing loss. Someone who describes themselves as half deaf will have a significant degree of hearing loss, but it's a very general, colloquial term, and could be slightly disparaging. There is no implication that hearing loss is 50%.

What does half deaf mean?

informal. unable to hear very well. He is half-deaf in one ear.

Who is the most famous deaf person?

Helen Keller was a remarkable American educator, disability activist and author. She is the most famous DeafBlind person in history. In 1882, Keller was 18 months old and fell ill with an acute illness which caused her to become deaf, blind and mute.