1 general:: Fortunate, enjoying success, as in You're in luck? we found your car keys. [Mid-1800s]
American Heritage Idioms
2 general:: Phrase(s): in luck fortunate; lucky. • You want a red one? You’re in luck. There is one red one left. • I had an accident, but I was in luck. It was not serious.
McGrawhill's American Idioms And Phrasal Verbs