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
a closed plane curve resulting from the intersection of a circular cone and a plane cutting completely through it; "the sums of the distances from the foci to any point on an ellipse is constant"
a conveyance that transports the letters and packages that are conveyed by the postal system
the system whereby messages are transmitted via the post office; "the mail handles billions of items every day"; "he works for the United States mail service"; "in England they call mail `the post'"
the bags of letters and packages that are transported by the postal service
any particular collection of letters or packages that is delivered; "your mail is on the table"; "is there any post for me?"; "she was opening her post"
cause to be directed or transmitted to another place; "send me your latest results"; "I'll mail you the paper when it's written"
send via the postal service; "I'll mail you the check tomorrow"