light speed

or light·speed

[ lahyt-speed ]

noun
  1. Physics, Optics. speed of light (def. 1).

  2. an extremely fast rate: The rumor circulated at light speed around the town.

adjective
  1. very fast: Her best time in the race is a lightspeed 8.7 seconds.

Origin of light speed

1
First recorded in 1855–60

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024

How to use light speed in a sentence

  • Again a tiny ship entered Thett's far-flung atmosphere, and slowed to less than a light speed, and sent its signal call ahead.

    Invaders from the Infinite | John Wood Campbell
  • Either the standard, multiple light-speed overdrive could be used, or the newer and vastly slower one, but not both together.

    Talents, Incorporated | William Fitzgerald Jenkins