From Hull AWE
The word belay, which can be used as a verb or a noun has two different pronunciations with the two occupations which use it - both, nowadays, essentially leisure occupations for most of us. (OED lists many more meanings, mostly obsolete.)
- In the world of sailing, where the verb is more common, belay has the stress on the second syllable: 'b'-LAY', IPA: /bə ˈleɪ/. Though this is current in the Royal Navy, it is yet more widely used in the field of leisure sailing. The meaning is 'to fasten [a rope] securely, by coiling or looping or knotting it round some fastening [e.g. a cleat]'; hence, by extension, 'to stop'. Admiral William Henry Smyth gave these examples, in his The Sailor's Word-book: an alphabetical digest of nautical terms of 1865 (cited in OED: "Belay there, stop! that is enough! Belay that yarn [sc. story], we have had enough of it!"
- For many in the world of mountaineering and climbing, where the word is more often used as a noun, a belay has the stress on the first syllable: 'BEE-lay', IPA: /ˈbiː leɪ/.