four-leaf clover
From Longman Dictionary of Contemporary Englishfour-leaf cloverˌfour-leaf ˈclover (also four-leaved clover British English) noun [countable] DLGROMa clover plant that has four leaves instead of the usual three, and is considered to be luckyExamples from the Corpusfour-leaf clover• As I was walking back up the hill, I found a four-leaf clover.• It has a long creeping rhizome from which leaves similar to a four-leaf clover develop in two rows.