light speed

Or light·speed

[lahyt speed]

noun

1. Physics, Optics.,  speed of light.

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.

Word History and Origins

Origin of light speed¹

First recorded in 1855–60