The term 'BIG CAT SIGN' can be solved by the three letter word 'LEO'. This is an abbreviation for the constellation LEO, which is one of the 88 constellations in space. It is also known as the Lion, and is one of the most recognizable constellations due to its large size and bright stars. The constellation is associated with the mythological figure of the Nemean Lion, a creature that was slain by Hercules.