This glossary entry tells the tale of a ghost, a pseudo technical term of Middle English poetics, conjured into being (well, so I would argue) by well-meaning lexicographers. The Middle English Dictionary defines raf as ‘crude, worthless verse; a pejorative term for alliterative poetry’. The Oxford English Dictionary goes a little further, glossing raff as ‘Alliteration; verse, esp. alliterative verse, of a crude kind, or in which sound is more prominent than sense; an instance of such verse.’