Definition of free-run in English:

free-run

verb

  • 1no object Of a signal generator, timepiece, etc.: to operate independently, without external influence or intervention. Also in extended use: to run freely, loosely, or easily.

  • 2no object Biology. Of a circadian rhythm: to operate in the absence of, or independently of, light or other external cues indicating the time of day. Also (of an organism): to maintain a circadian rhythm in this way.

Origin

1940s. From free + run.

Pronunciation

free-run

/ˌfriːˈrʌn/