The term 'not easily understood' can be described by three crossword solutions: DEEP (4 letters), OPAQUE (6 letters), and OBSCURE (7 letters). DEEP implies a level of complexity that requires a great deal of thought to comprehend. OPAQUE suggests something that is difficult to see through, or not easily understood. OBSCURE implies something that is not well known or hard to comprehend. All three words suggest that the subject matter is not easily understood.