air passage provided by a retractable device containing intake and exhaust pipes; permits a submarine to stay submerged for extended periods of time
breathing device consisting of a bent tube fitting into a swimmer's mouth and extending above the surface; allows swimmer to breathe while face down in the water
uneducated in the fundamentals of a given art or branch of learning; lacking knowledge of a specific field; "she is ignorant of quantum mechanics"; "he is musically illiterate"
uneducated in general; lacking knowledge or sophistication; "an ignorant man"; "nescient of contemporary literature"; "an unlearned group incapable of understanding complex issues"; "exhibiting contempt for his unlettered companions"
unaware because of a lack of relevant information or knowledge; "he was completely ignorant of the circumstances"; "an unknowledgeable assistant"; "his rudeness was unwitting"