os·me·te·ri·um 
(ŏz′mĭ-tîrē-əm)
(ŏz′mĭ-tîrē-əm)n. pl. os·me·te·ri·a (-tîrē-ə)
An eversible organ behind the head of certain caterpillars, containing strong-smelling chemicals that deter predators.
[New Latin osmētērium, from Greek osmē, smell.]