Wiktionary
n. 1 The language of a Native or Aboriginal people (often capitalized). 2 One's first language, learned in early childhood.
WordNet
n. the language that a person has spoken from earliest childhood
Usage examples of "native language".
He had drilled himself, to the point of unconscious use, in the native language of this area.
A pilot, by tradition too toploftical to speak to any lesser rating than a ship's master, could have been expected to rebuff such a thing as a mere passenger, but this pilot seemed surprised and pleased to be accosted in his native language by a foreigner.
The survival of modern Africa's four native language families (that is, the four other than the recently arrived Austronesian language of Madagascar) isn't due to the intrinsic superiority of those languages as vehicles for communication.
Once we were completely set up, the only people the locals would have to deal with would be someone speaking something close to their own native language, and not in the foreign German tongue.
Realms render messages, either in common or their native language.
Runs-red-Talking had spent many days immersing himself in native language study, usually finishing at or near the top of his study group, but in the shock of the moment his knowledge deserted him.