from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. An aromatic hydrocarbon based on benzene with two methyl substituents bonded to adjacent carbon atoms in the aromatic ring (the ortho configuration).
from the GNU version of the Collaborative International Dictionary of English
- n. That variety of xylene (C6H4(CH3)2) in which the two methyl groups are in the ortho position; a colorless, liquid, combustible hydrocarbon resembling benzene.
ortho- + xylene (Wiktionary)