Wats it mean when a guy...........?

Makes a < sign with his fingers and sticks his toungue in it???? It's like some hand sign I asked some people at school but they wouldn't tell me they just told me it meant something gross. Why would I ask??? Cuz wen I was walkin in the halls a guy that's my friend did that hand sign to me O.o (btw I'm 13) don't be shy I need to know if I need to know!!! :P