Word of the Day
5 February 2026
cotter
A pin or wedge inserted through a slot to hold machine parts together.
Why this one
Worth separating from the split pin many people call a cotter pin: a true cotter is a tapered wedge driven through a slot so it takes load, not just a bit of wire stopping a nut from backing off. Old bicycle cranks were held on the same way.
In use
That crank's been slipping for weeks, so knock the cotter out and let's see if the flat's worn round.
Written by our editors to show how the term is used, not a recorded quotation.