de·fin·i·ens 
(dĭ-fĭnē-ĕnz′)
(dĭ-fĭnē-ĕnz′)n. pl. de·fin·i·en·ti·a (-ĕnshē-ə, -shə)
The word or words serving to define another word or expression, as in a dictionary entry.
[Latin dēfīniēns, present participle of dēfīnīre, to define; see DEFINE.]