Source : Webster's Revised Unabridged Dictionary (1913)

Clypeus \Clyp"e*us\, n.; pl. {Clypei}. [L., a shield.]
   (Zo["o]l.)
   The frontal plate of the head of an insect.

Source : WordNet®

clypeus
     n : a shield-like plate on the front of an insect's head
     [also: {clypei} (pl)]