coppernoun(METAL)
B2[ U ]
a chemical element that is a reddish-brown metal, used especially for making wire and coins:
They mine a lot of copper around these parts.
One of the properties of copper is that it conducts heat and electricity very well.
[ U ]
the reddish-brown colour of the metal copper:
The copper of Rosie's hair shone in the sunlight.
[ C usually plural ]
a brown coin of low value:
I gave him a few coppers.