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
outward features; "he enjoyed the solemn externals of religion"
happening or arising or located outside or beyond some limits or especially surface; "the external auditory canal"; "external pressures"
purely outward or superficial; "external composure"; "an external concern for reputation"- A.R.Gurney,Jr.
from or between other countries; "external commerce"; "international trade"; "developing nations need outside help"
coming from the outside; "extraneous light in the camera spoiled the photograph"; "relying upon an extraneous income"; "disdaining outside pressure groups"