n 1  :  any of numerous unctuous combustible substances that are liquid or can be liquefied easily on warming, are soluble in ether but not in water, and leave a greasy stain on paper or cloth - see ESSENTIAL OIL FATTY OIL VOLATILE OIL   2  :  a substance (as a cosmetic preparation) of oily consistency <bath >  oil adj 
 
 
 
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