I could find no official definition of this word from Dracula. It appears in the expression ‘bloofer lady’, referring to Lucy Westenra. It’s pretty obvious from the text that it’s a childish rendition of ‘beautiful’ (the vampire Lucy abducts and feeds on Hampstead children, and this is how they describe her). Stoker’s use of it may well have been influenced by the ‘boofer lady’ – Bella Wilfer – in Dickens’s Our Mutual Friend.