ˈdīˌk]ēd.(ˌ)ō, dī|k]+ noun
Etymology: International Scientific Vocabulary diketo- + piperazine
1. : a crystalline compound C 4 H 6 N 2 O 2 that is obtainable from two molecules of glycine by dehydration and may be regarded as a cyclic dipeptide; 2,5-piperazine-dione
2. : any of various cyclic compounds formed similarly to diketopiperazine from alpha-amino acids other than glycine or obtained by partial hydrolysis of proteins