means The smallest unit of a chemical compound, made of two or more atoms bonded together, that still retains the properties of that substance.

from From French 'molécule,' borrowed in the 18th century from the scientific Latin coinage 'molecula' — a diminutive of Latin 'moles,' meaning 'mass' or 'bulk.' So the word literally tags it as a 'tiny mass,' a little lump of matter. That same 'moles' gave us 'molar' and lurks inside 'demolish' (to un-mass something) and 'molest' (originally 'to burden'). The term spread through the new chemistry of the era as scientists needed a name for matter's smallest meaningful clumps.