•
to balance one influence against an opposing influence, so that there is no great difference as a resultThe extra cost of travelling to work is offset by the lower price of houses here.
UK He keeps his petrol receipts because petrol is one of the expenses that he can offset against tax (= can show to the government as being a business cost, and so not pay tax).
•
to pay for things that will reduce carbon in order to reduce the damage caused by carbon that you produceWe offset all our long-haul flights.