From free +‎ wheel.

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freewheel (plural freewheels)

1. A device in a transmission that disengages the driveshaft from the driven shaft when the driven shaft rotates faster than the driveshaft.
2. The mode or state of operation thus produced: Synonym of neutral.

• free wheel

freewheel (third-person singular simple present freewheels, present participle freewheeling, simple past and past participle freewheeled)

1. (engineering, mechanics, of a gear) To continue spinning after disengagement.
2. (bicycling, of a cyclist) To ride a bicycle without pedalling, e.g. downhill.
   • 1935, George Orwell, chapter 3, in A Clergyman’s Daughter‎^[1]:

     On her elderly bicycle with the basketwork carrier on the handle-bars, Dorothy free-wheeled down the hill, doing mental arithmetic with three pounds nineteen and fourpence--her entire stock of money until next quarter-day.

3. (automotive, of a motorist) To operate a motor vehicle which is coasting without power, e.g. downhill.
   • 1983, Bill Oddie, Gone Birding, London: Methuen, page 78:

     Silently and gracefully I free-wheeled across the path of three juggernauts, [...] glided across the hard shoulder and came to rest halfway up a grass bank.

4. (figuratively, by extension) To operate free from constraints.

• → Dutch: freewheelen