No rocket scientist is an idiom used to describe someone who is not particularly intelligent or knowledgeable. The term can be broken down into three crossword solutions: DOLT (4 letters), DOPE (4 letters), and DENSE (5 letters). DOLT is a slang term for a stupid person, while DOPE is another slang term for an idiot or fool. DENSE is a synonym for thick or stupid. All three words are used to describe someone who is not particularly intelligent or knowledgeable.