Longman Dictionary of Contemporary English
four-leaf clover
noun
EXAMPLES FROM CORPUS
▪ 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.
Wiktionary
four-leaf clover
n. 1 An uncommon variation of the clover, having four leaves instead of the usual three. 2 (context idiomatic English) A bringer of good luck
Wikipedia
Four-leaf clover
Usage examples of "four-leaf clover".
I make a show of examining her, but, as much as I want to smile, I can't keep from frowning at the gold, four-leaf clover charm dangling from her necklace, the emerald inset in its center.
A four-leaf clover, rowan berries, looking at yourself through a rock with a natural hole.
At each place was a napkin, folded to resemble a four-leaf clover.