ˈōlēəm noun
( plural olea -ēə ; or oleums )
Etymology: Latin — more at oil
1. plural olea : oil — used chiefly in phrases that are the Latin names of oils
oleum thae piperitae
2. plural oleums : a heavy oily strongly corrosive liquid that consists of a solution of sulfur trioxide in anhydrous sulfuric acid, that fumes in moist air and reacts violently with water with the evolution of heat, and that is used chiefly in sulfonation and sulfation processes, in mixed acid for nitration, and in petroleum refining — called also fuming sulfuric acid
the strength of oleum is designated as percent by weight of free sulfur trioxide: thus 20 5 oleum contains 20 5 SO 3 and 80 5 H 2 SO 4 by weight — B.M.Carter