Definition of citrulline in US English:

citrulline

(also citrullin)

noun

  • Biochemistry. Now usually citrulline. An α-amino acid (originally isolated from watermelon, Citrullus vulgaris) found widely in living cells as an intermediate in the synthesis of arginine and in the conversion of ammonia to urea.

Origin

Late 19th century (in an earlier sense). From scientific Latin Citrullus + -ine, perhaps originally after German Citrullin, † Citrullinum.