The term BUSILY WORKING can be broken down into four words: HUM (3 letters), PLIES (5 letters), PLY (3 letters), and PLIED (5 letters). HUM is a verb meaning to make a low, continuous sound. PLIES is a verb meaning to apply or spread something over a surface. PLY is a noun meaning a thickness or layer of something. Lastly, PLIED is a verb meaning to apply or spread something over a surface. All together, these words describe someone who is busily working, making a low sound while applying or spreading something over a surface in layers.