The term 'SEAL UP' can be broken down into three separate words: SHUT (4 letters), CAULK (5 letters), and ENTOMB (6 letters). To 'seal up' something means to close it off completely, often in order to protect it from outside elements. To 'SHUT' something is to close it, usually with a door or lid. To 'CAULK' something is to fill in the gaps between two surfaces with a sealant, such as silicone or tar. Finally, to 'ENTOMB' something is to place it in a sealed chamber, such as a coffin or a tomb. In summary, the term 'SEAL UP' refers to the act of completely closing off an object or space, either by shutting it, filling in the gaps, or placing it in a sealed chamber.