Maleic acid
WordNet
noun
(1) A colorless crystalline compound found in unripe fruit (such as apples or tomatoes or cherries) and used mainly to make polyester resins
WiktionaryText
Noun
maleic acid
- an unsaturated organic dicarboxylic acid, HOOCCH=CHCOOH, the geometric isomer of fumaric acid; it is found in unripe fruit, and is used industrially in the production of polyester resins