Hi Anna, Just as how the previous user has answered, 날고 is not a complete word or a sentence. It is a conjugation of a verb 날다 (to fly) and 날고 roughly translates to "(I/s/he/you, etc.) flies and.." It's not a complete word, we need to look or hear the rest of the sentence.

You need more contest. 날다 has several different meanings, although a major one is "to fly". And -고 is a connective ending that has different meanings, again depending on context.