/nay"li dik"sik, nay'-/ , Pharm.
a substance, C 12 H 12 N 2 O 3 , that has antibacterial activity against many susceptible Gram-negative organisms, esp. used in the treatment of urinary tract infections.
[ 1960-65; by shortening and rearrangement of naphthyridine and carboxylic acid, components of its chemical name ]