semicarbazone

from The Century Dictionary.

• noun A compound formed by the action of semicarbazin on an aldehyde or a ketone, as the semicarbazone of acetaldehyde, CH₃CH:NNHCONH₂. Such compounds are usually crystalline and are used to isolate or identify aldehydes or ketones.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun organic chemistry The reaction product of an aldehyde or ketone with semicarbazide; they have the general formula R1R2C=N-NH-CO-NH2