also: うんがよい
expression, i-adjective (yoi/ii class)
Describes a person or situation favored by chance. Often used in exclamations or to comment on good fortune.
今日は本当に運がいい。
I'm really lucky today.
運がいいことに、電車が遅れなかった。
Fortunately, the train wasn't delayed.
Phrase consisting of 運 (luck) + が (subject marker) + いい (good). A straightforward adjectival expression.