Other forms: cunningest; cunninger; cunnings
In fairy tales, always watch out for the cunning fox or the cunning witch. Cunning means clever, in the sense of trickery. A cunning plan might involve setting traps for the innocent and pure at heart to fall into.
This adjective goes back to the 14th-century English verb cunnen, which meant "to know," and is actually related to our English verb know. In earlier times, the noun was used to mean a high level of skill in using the hands. You can be cunning, but you can also use your cunning to figure out a very clever and tricky plan.