Underway: A US Navy term meaning that the ship has pulled out of port and is out to sea. Also refered to as "Hazed, grey, and underway."
Chief: "Well it's too late to try and get out of this det now son, We're underway."
by b--rad September 28, 2006
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It is actually 2 words - under way - and was originally a nautical term meaning that a ship had begun its journey.
Likely to have been of early British Naval origin.
Over time, it has also become a description of an event having started.
Hurry if you want to see the ship leave, because it will soon be under way (not underway.)

The search for the missing child is already under way (not underway.)
by Authorwise May 3, 2011
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Homosexual acts are acceptable - indeed, not gay at all - if performed on a naval vessel away from port.
"I licked the Able Seaman's balls while he came on my face, but it's not gay if you're underway, am I right?"
by Cpt. Jack Hoff October 18, 2007
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