The term 'Dull Sound' can be described by a variety of words, including 'CLONK' (5 letters), 'THUD' (4 letters), 'CLUNK' (5 letters), 'THUMP' (5 letters), 'thunk' (5 letters), 'THRUM' (5 letters), and 'schwa' (5 letters), as well as 'PLOP' (4 letters). All of these words describe a sound that is not particularly loud or sharp, but rather dull and muffled. CLONK, THUD, CLUNK, THUMP, thunk, THRUM, schwa, and PLOP are all examples of onomatopoeia, which are words that imitate the sound they represent.