from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A bolt, wedge, key, or pin inserted through a slot in order to hold parts together.
  • n. A cotter pin.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A pin or wedge inserted through a slot to hold machine parts together.
  • n. Erroneously, sometimes used of a cotter pin.
  • v. To fasten with a cotter.
  • n. A peasant who performed labour in exchange for the right to live in a cottage.

from the GNU version of the Collaborative International Dictionary of English

  • n. A cottager; a cottier.
  • n. A piece of wood or metal, commonly wedge-shaped, used for fastening together parts of a machine or structure. It is driven into an opening through one or all of the parts. [See Illust.] In the United States a cotter is commonly called a key.
  • n. A toggle.
  • transitive v. To fasten with a cotter.

from The Century Dictionary and Cyclopedia

  • To fasten by means of a cotter.
  • n. A cottager; in Scotland, one who dwells in a cot or cottage dependent upon a farm. Sometimes a piece of land is attached to the cottage.
  • n. In mech., a wedge-shaped piece of wood or iron used as a wedge for fastening or tightening.
  • n. Cotters were used in place of the nut and thread on a bolt before the cutting of threads was easy and cheap, and are still useful where the thread would be liable to injury. A wedge-shaped or tapered flat pin (cotter) is driven into a slot cut near the end of the bolt or stud, drawing up the bolt. A similar device is used to secure nuts on bolts from being shaken off. A hole is drilled through the bolt, at right angles to its axis, beyond the nut, and through this hole a taper pin is driven. The cotter in this case is often split at its smaller end, and if the two parts are spread it cannot of itself work out. In small work the cotter is made of half-round wire, bent double on itself, with an eye at the bend, so that when it is in place and the ends are spread, it cannot slip out either way. The hole can therefore be straight or cylindrical and not tapering, and the cotter has no wedging action in this form. Cotters are much used in motorcar construction.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. fastener consisting of a wedge or pin inserted through a slot to hold two other pieces together
  • n. a peasant farmer in the Scottish Highlands
  • n. a medieval English villein


from The American Heritage® Dictionary of the English Language, 4th Edition

Origin unknown.


  • a cotter is a thief; he that lifts a drove from a Sassenach laird is a gentleman-drover.

    The Waverley

  • The fire crackles and blazes, so that we do not mind the wind, though there are no blinds to the kitchen, and if we do not "cotter" the shutters, we look out upon the black night, and the tall Scotch pine that has been tossed so wildly for so many years, and is not torn down yet.

    Six to Sixteen: A Story for Girls

  • It patches waders, boats, holds together broken rods, makes pretty nifty sunglass retainers (like above), and just a week or so ago I actually used duct tape to hold my oar lock in place after a friend had straightened the cotter pin holding it in place. 12 inches if Duct tape literally saved an entire day of fishing.

    If you can't Duct it...

  • I have used cotter pins that are around 4 inches long to hold wicks in the center while candles are hardening/setting up.

    Off Center Wick

  • “You look like air,” Larry said as he hung the bait on a hook in the ceiling; the hook was cabled to a cotter pin in the trapdoor, so if something pulled the bait, the gate would drop and lock.

    Blood Lite II: Overbite

  • Back when I was a kid, we had this fail-safe method for avoiding garage door accidents that was entirely cotter pin proof: Make sure nothing is under the door before you press the button.

    Monday, Jan. 26 – The Bleat.

  • And you had the duct tape right there in your hand and coulda wrapped that rebellious cotter pin until it suffocated.

    Monday, Jan. 26 – The Bleat.

  • Grenades have a small, removable cotter pin in the firing mechanism.

    Heart of a Patriot

  • July 6, 2009 at 9:27 am welclom bak *starts singing feem song to wlecom bak cotter*

    Once he was - Lolcats 'n' Funny Pictures of Cats - I Can Has Cheezburger?

  • Although it was a journey of more than 500 miles, it would have been one heck of a hail mary to knock the cotter pin loose, slide the hitch cover out, and miraculously pop the cotter pin back in.

    Dear Dishonest Ute Fan,


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