To treat or combine chemically an unsaturated compound with hydrogen. Liquid vegetable oils are often hydrogenated to turn them into solids.
To combine with or subject to the action of hydrogen, especially to combine (an unsaturated oil) with hydrogen to produce a solid fat.
To turn coal into oil by combining its carbon with hydrogen to form hydrocarbons.
To combine with, treat with, or expose to the action of, hydrogen; specif., to produce a saturated fat or trans fat by treating (an unsaturated fat) with hydrogen.