Sentence:  Production of <WSD>Tallboys</WSD> was limited to one a day in Britain, and although thirty per week were being made in America, the convoys bringing them over could be held up by bad weather and the continuing (if decreasing) threat from U-boats. 
Meaning of the word marked with <WSD> tags:  An (earthquake bomb) developed for the (British Armed Forces) and deployed by the RAF during World War II.