The term 'stiffly formal' can be broken down into four crossword solutions: PRIM (4 letters), STAID (5 letters), STILTED (7 letters) and STARCHY (7 letters). PRIM means to be excessively proper or PRIM in behavior, dress, or attitude. STAID means to be serious, solemn, and dignified. STILTED means to be stiffly formal or unnatural in manner or style. STARCHY means to be rigidly formal or conventional. All of these words describe a person or thing that is overly formal and rigid in their behavior, dress, or attitude.