Groon

A groon is a unit of measurement in the Generation 1 continuity family.

A groon is a cybertronian unit of time-measurement equal (or at least approximately equal to) an earth hour.

Fiction

Marvel Comics UK continuity

The Magnificent Six! Megadeath let his broken Autobot prisoners go with a neutronic blast imminent in two groons.

Retelling this event to Silverbolt in 1990, Jazz described the time as two hours.

From Teletraan I: The Transformers Wiki, a Wikia wiki.