Definitions
American Heritage® Dictionary of the English Language, Fourth Edition
- adj. Moving or directed away from the shore: an offshore wind.
- adj. Located at a distance from the shore: an offshore mooring; offshore oil-drilling platforms.
- adj. Located or based in a foreign country and not subject to tax laws: offshore bank accounts; offshore investments.
- adv. Away from the shore: The storm moved offshore.
- adv. At a distance from the shore: a boat moored offshore.
- n. The comparatively flat region of submerged land extending seaward from beyond the region where breakers form to the edge of the continental shelf.
Century Dictionary and Cyclopedia
- From the shore; away from the shore: as, the wind was blowing offshore.
- At a distance from the shore.
- Leading off or away from the shore.
- Belonging to or carrying on operations in that part of the sea which is off or at a distance from the shore, especially at a distance of more than three miles from the shore: opposed to inshore.
Wiktionary
- adj. Moving away from the shore.
- adj. Located in the sea away from the coast.
- adj. Located in another country, especially one having beneficial tax laws.
- adv. Away from the shore.
- adv. At some distance from the shore.
- v. To use foreign labour to substitute for local labour.
GNU Webster's 1913
- adj. From the shore
- adj. Located in the waters near the shore.
- adj. Operating or located in a foreign country.
WordNet 3.0
- adj. at some distance from the shore
- adv. away from shore; away from land
- adj. (of winds) coming from the land
Examples
“The action is captured in the forest of drilling rigs and endless pump jacks that, amid this year's slowly receding sloughs, seem to float on water, giving new meaning to the term "offshore drilling.”
“Since these spots were located offshore, the term offshore banking refers to the act of opening account outside the original boundaries of jurisdiction.”
“ROMANS.(on camera): This the first time that "U.S. News & World Report" editors have considered what they called offshore resistance in their best careers categories.”
“My next guest is introducing legislation in the Senate to keep jobs in this country and to extend government benefits to service workers who are hit by what he calls offshore outsourcing.”
“Industry observers believe the state's handle, or sports books 'hold on the Super Bowl has been dropping annually because there are more opportunities for people to place their bets on the big game elsewhere, namely in "offshore" sports books, which allow bettors to place their wagers over the phone or on the Internet.”
“Short-term offshore debt rose $1.3 billion in the second quarter to $149.7 billion, the Bank of Korea said Tuesday, a sharp slowdown from the $13.5 billion increase in the first quarter.”
The Wall Street Journal: Growth in Korea's Short-Term Debt Slows
“Now if we could just get Rush to pay his taxes on all the money hes hiding in offshore accts, we could fix the deficet in a week.”
“Now as a middle class person, I am not a fan of wealth-redistribution, because it really causes more and more people to start to hide money offshore from the Government and in the end causes more issues.”
“As part of the conspiracy, U.S. authorities allege the bankers opened accounts in the name of offshore sham corporations and foundations in order to avoid detection, including entities formed under the laws of Liechtenstein, Panama and Hong Kong.”
The Wall Street Journal: Swiss Bank Wegelin Indicted on U.S. Tax Charges
“First, he proposed raising the $75 million liability cap for companies operating in offshore US waters.”
The Huffington Post: Robert L. Cavnar: The Coming Showdown Over America's Energy Future
Lists
These user-created lists contain the word ‘offshore’.
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Hydrocarbon Energy Exploration/Extraction Terms
A list of terms encountered in the jargon of hydrocarbon exploration, mapping, and extraction.
hydrofracking, hydraulic fracturing, drilling, borehole, rig, formation, shale, coal, marl, seismic, horizontal drilling, unconventional ga... and 77 more...

qroqqa In the financial sense the OED has examples going as far back as 1929, and they just mean "abroad, foreign". There's no sense that—as one might guess—it began with actual off-shore territories like Guernsey and was then extended to other tax havens. Sep 12, 2008
yarb Actually one might offshore something to Luxembourg (for example; I don't know whether Liechtenstein is tax-friendly enough). Offshore is a byword for "low-tax environment" - most of these environments are islands but insularity isn't a requisite.
Speaking of Luxembourg, what a football result for them last night, defeating Switzerland, in Switzerland, in a European qualifier. They'll have been dancing in the streets of... Luxembourg last night! Sep 11, 2008
rolig In the tax haven sense, then, the verb "offshore" does not mean "send into the territorial waters of" a country, but send out of a country, presumably to some island nation/territory like the Caymans. I suspect people do not offshore operations to Liechtenstein, however tax-friendly that Alpine principality might be. I wonder if this usage will ever reach the general population, as in "We're planning to offshore ourselves to Bermuda for a couple of weeks this summer." Sep 11, 2008
yarb It's also used as a verb, in finance, meaning "to move an operation offshore", i.e. to a tax haven. Sep 11, 2008
rolig Interesting. I don't think I have come across this as a preposition before. I agree it sounds barbarous. I would have said, more wordily, "off the coast of Angola" and something like "in Romania, both on land and offshore". I expect this prepositional usage is fairly specialized, confined to those who deal with offshore activities, in other words, it's professional argot. Sep 11, 2008
qroqqa This preposition can be used transitively in the oil and gas context, e.g.
Exxon Mobil Corporation announced today that its subsidiary, Esso Exploration Angola (Block 15) Limited (Esso), has started production of the Xikomba deepwater development offshore Angola Block 15. Xikomba is the company's first production on Block 15 and represents the first of several anticipated operated production facilities offshore Angola.
—www.GulfOilandGas.com
Sounds a bit barbarous to me, but who am I to argue with a new argument structure? The OED has examples of this usage back to 1967.
(Oh, and now I've found a live example of 'onshore' likewise used: 'farm-out transactions onshore and offshore Romania'.) Sep 11, 2008