Hullo is a greeting or call for attention, written the older British way. Hullo there, said hullo, hullo again.
It is a spelling variant of hello with a u, and it looks Edwardian on the page, which is why it survives mostly in older fiction. Hullo also carries a note of surprise, as in hullo, what is this.
1nounhulloA greeting or call for attention, written in the older British way with a u where the usual spelling has an e.
“He called out a cheerful hullo from the garden gate.”
hullo is a greeting.
Practised in A Song of Ice and Fire