Speed of light

According to Dictionary.com the definition of light speed is:

"The distance light can travel in a unit of time through a given substance. Light travels through a vacuum at about 186,000 miles, or 300,000 kilometers, per second."

The accurate speed of light is: 299 792 458 m/s

I would define it as:

Speed of light is the maximun speed which all form of information in the universe can travel. Though the speed is mostly known as light, it is actually the speed that all massless particles travel in a vaccum. Including electromagnetic waves.

All electromagnetic waves travel at light speed through a vacuum. Space is the only vacuum known to man, and is therefore the only example of where, we can see the speed of light in electromagnetic waves. Check this page for more info about SPACE!