light speed

American  

[lahyt speed] / ˈlaɪt ˌspid /

Or lightspeed

noun

1. Physics, Optics. speed of light.

2. an extremely fast rate.

   The rumor circulated at light speed around the town.

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adjective

1. very fast.

   Her best time in the race is a lightspeed 8.7 seconds.

Etymology

Origin of light speed

First recorded in 1855–60

Example Sentences

That is swift on Earth but slow compared with winds near the Eddington limit around supermassive black holes, where outflows can reach 20 to 30 percent of light speed, more than 200 million km/h.

From Science Daily • Nov. 10, 2025

Beyond a certain point—roughly 800 square millimeters, or 1.25 square inches—the laws of light and light speed prohibit larger designs.

From The Wall Street Journal • Nov. 3, 2025

In an aptly titled Associated Press news story “Trump moves with light speed and brute force in shaking the core of what America has been”, Calvin Woodward recounts the last six weeks:

From Salon • Feb. 27, 2025

And they can do it all at light speed.

From Los Angeles Times • Nov. 6, 2023

Spacecraft that could travel at light speed were rare, and they required fuel to operate.

From "Ready Player One: A Novel" by Ernest Cline