Which word on this page has the highest character count?The biggest word you could derive from words that start with 'r' and include 'def' is 'redefinitions', which consists 13 letters.
How many viable words are possible to make using this combination of letters?One can make 19 words from the combination you specified.
What is the best score you can get in Scrabble from this list of words that start with 'r' and include 'def'?You could make 'redefy' which scores 13 in Scrabble.