The term 'stupid and silly' can be described by the crossword solutions of VACUOUS (7 letters), INANE (5 letters), and GOOFY (5 letters). VACUOUS means having or showing a lack of thought or intelligence, while INANE means lacking sense or meaning. GOOFY, on the other hand, is an adjective used to describe someone who is silly or slightly foolish. All three words are used to describe someone or something that is not very intelligent or serious.