This is a constant representing the value negative infinity. It should be identical to a negative sign placed in front of the Infinity value provided as a property of the Global object in an ECMA-compliant implementation. Refer to the Infinity topic for further discussion.
ECMA 262 edition 2 - section - 22.214.171.124
ECMA 262 edition 3 - section - 126.96.36.199