"Spoonhead" is a racist term in Federation Standard used to refer to the Cardassian species in a derogatory manner in the 24th century. The term refers to the spoon-like oval in the Cardassian cranial structure. (DS9 episodes: "Things Past", "Empok Nor", "Wrongs Darker Than Death or Night")

Spoonhead article at Memory Alpha, the wiki for canon Star Trek.