Treacle Treacle treacle (countable and uncountable, plural treacles) (chiefly Britain) A syrupy byproduct of sugar refining; molasses or golden syrup. https://en.wiktionary.org › wiki › treacle treacle - Wiktionary (/ˈtriːkəl/) is any uncrystallised syrup made during the refining of sugar. The most common forms of treacle are golden syrup, a pale variety, and a darker variety known as black treacle, similar to molasses.