Symbol for the Andromeda Galaxy?

There is no symbol in astonomy or astrology for the Andromeda Galaxy, but it is also known by the names Messier 31 (or M31) and NGC 224, and formerly as the Andromeda Nebula, before its nature was understood. If you mean the symbol for Andromeda's shape, it's Sb, representing that is a spiral galaxy with an intermediate degree of spiraling.