1. Plural of lightspeed; the speed of light in a vacuum, approximately 299,792 kilometers per second or 186,282 miles per second, often used as a unit of measurement in physics and science fiction.
Usage: Usually used in plural form when referring to multiple instances, comparisons, or theoretical multiples of the speed of light.; Common in physics, astronomy, and science fiction contexts.

Examples

• In science fiction, spaceships often travel at fractions of lightspeeds to reach distant stars.
• The physicist explained that nothing with mass can accelerate to lightspeeds according to Einstein's theory of relativity.
• Theoretical warp drives might allow travel at multiple lightspeeds without violating the laws of physics.
• Radio signals travel at lightspeeds, making instant communication across space theoretically possible.
• The novel imagined a future where humanity had mastered propulsion systems capable of achieving lightspeeds.