In physics, what is the symbol that looks like a horseshoe, and relation to voltage
It's a horseshoe.
The horseshoe was used as protective and good luck symbol this goes back many centuries
The upside down horseshoe symbol is of Greek origin and is used to calculate many different types of problems. The symbol expresses the unlucky nature of the problem at hand.
You have a tire low on air.
An ohmmeter measures ohms. These are the measurement of electrical resistance. The symbol for ohms is the capital Omega symbol, a symbol that resembles an upside down horseshoe.
A horseshoe, four-leaf clover and the chimney sweeper.
That would be Omega (Ω) , the Greek capital letter.
Is that the Ω (ohm) symbol you are referring to? An ohm is the unit of electric resistance.
I think it is the amount of air in your tires
That is not a horseshoe. It represents a tire. The light is on because one or more tires is low of air pressure. All this is listed in your owners manual.