Definition of mesityl in US English:

mesityl

noun

Chemistry
  • A cyclic hydrocarbon group or radical derived from mesitylene, either (CH₃)₂C₆H₃CH₂— (3,5-dimethylbenzyl) or (now usually) specifically (CH₃)₃C₆H₃— (2,4,6-trimethylphenyl). Usually attributive or as a formative element in chemical names.

Origin

Mid 19th century (in an earlier sense). From mesite + -yl.