u·re·din·i·um 
(yr′ĭ-dĭnē-əm) also u·re·di·um (y-rēdē-əm)
(yr′ĭ-dĭnē-əm) also u·re·di·um (y-rēdē-əm)n. pl. u·re·din·i·a (-dĭnē-ə) also u·re·di·a (-dē-ə)
A reddish pustulelike structure that is formed in the tissue of a plant infected by a rust fungus and produces urediniospores.
[New Latin ūrēdinium, from Latin ūrēdō, ūrēdin-, blight, from ūrere, to burn.]