Thousand was a number equal to 10 times 100.
On Talos IV, thousands of centuries before 2254, a war devastated the planet's surface, forcing the Talosians underground. (TOS: "The Cage")
In 2254, thousands of Talosians were probing the thoughts of Captain Christopher Pike. (TOS: "The Cage")
In 2269, the immortal Flint put the crew of the USS Enterprise into suspended animation, with the intention of keeping them there for a thousand to two-thousand years. (TOS: "Requiem for Methuselah")
In 2368, the planet Penthara IV was slowly turning to ice which would result in thousands, maybe tens of thousands of deaths, in a matter of weeks if not stopped. (TNG: "A Matter of Time")