Final answer:
The word 'fortuitous' is most similar in meaning to 'lucky', indicating something happening by chance in a beneficial way.
Step-by-step explanation:
The word fortuitous is most similar in meaning to the word lucky. When we describe something as fortuitous, we are saying that it has happened by chance in a happy or beneficial way.
It does not carry the connotations of bravery that courageous does, nor does it imply something constant like continuous, or something deserving attention like noteworthy.