The term 'Silly Billy' is a phrase used to describe someone who is foolish or silly. The crossword solutions for this term are FOOL (4 letters), ASS (3 letters), and GOOF (4 letters). FOOL is a noun that means a person who acts unwisely or without good sense. ASS is a noun that means a stupid or foolish person. GOOF is a noun that means a silly, foolish, or stupid person. All three words can be used to describe someone who is silly or foolish, such as Silly Billy.