Lucky, a. [Compar. Luckier; superl. Luckiest.]
1. Favored by luck; fortunate; meeting with good success or good fortune; -- said of persons; as, a lucky adventurer. " Lucky wight." Spenser.
2. Producing, or resulting in, good by chance, or unexpectedly; favorable; auspicious; fortunate; as, a lucky mistake; a lucky cast; a lucky hour. We doubt not of a fair and lucky war. Shak.
Syn. -- Successful; fortunate; prosperous; auspicious.
Shades of meaning
Fernald has no entry of its own for lucky; he lists it under fortunate, happy.
Where he writes about it:
A man is successful in any case if he achieves or gains what he seeks; he is known as a successful man if he has achieved or gained worthy objects of endeavor; he is fortunate or lucky if advantages have come to him without or beyond his direct planning or achieving. — from fortunate
Lucky is the more common and colloquial, fortunate the more elegant word; fortunate is more naturally applied to the graver matters, as we speak of the fortunate, rather than the lucky, issue of a great battle; lucky more strongly emphasizes the element of chance, as when we speak of a lucky hit, a lucky guess, or of one as "born under a lucky star." Favored is used in a religious sense, implying that one is the object of divine favor. — from fortunate
In this sense happy is closely allied to fortunate and lucky. (See fortunate.) Happy has, however, so far diverged from this original sense as to apply to advantages where chance is not recognized, or is even excluded by direct reference to the divine will, when it becomes almost equivalent to blessed. — from happy