also: うんのよい
expression, i-adjective (yoi/ii class)
Describes a person or situation that has good luck. Often used in set phrases like 運のいいことに (luckily).
See also: 運がいい
彼は運のいい男だ。
He is a lucky man.
運のいいことに、電車に間に合った。
Luckily, I caught the train.
運がいい is a more common and flexible phrase meaning 'lucky', while 運のいい functions as a prenominal modifier (e.g., 運のいい人).
Phrase composed of 運 (luck) + の (possessive particle) + いい (good).