trans fatty acid

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An unsaturated fatty acid produced by the partial hydrogenation of vegetable oils and present in hardened vegetable oils, most margarines, commercial baked foods, and many fried foods. An excess of these fats in the diet is thought to raise the cholesterol level in the bloodstream.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun An unsaturated fatty acid in which one or more of the double bonds has the trans orientation instead of the usual cis orientation.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a fatty acid that has been produced by hydrogenating an unsaturated fatty acid (and so changing its shape); found in processed foods such as margarine and fried foods and puddings and commercially baked goods and partially hydrogenated vegetable oils