What is pluto symbol?

The symbol for Pluto is ♇. It's a glyph that's a combination of the letters P and L, representing Pluto's initials but is also interpreted as representing the astronomer Percival Lowell, who predicted Pluto's existence. It can also be seen as a cross below a circle (representing spirit) above a crescent (representing soul), combining the other planet symbols and therefore representing the underworld.