Speaking of lines - we discussed sheets, etc. - there are actually quite a few different types of lines.

sheets - line used to haul sails
shrouds - main lines used in the rigging
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Sorry Hyla, but I'm going to have to disagree with you on the subject of shrouds. Shrouds are static rigging - ie, they are used to hold the mast up and to induce certain bend characteristics into the mast to achieve the otpimum sail shape and gust response for the conditions. Because of this, they cannot be likened to sheets or halyards, which are running rigging.

Some other more 'slang-like' nautical terms would be:
'Honking Billy' - when the wind is absolutely howling
'Like being in a washing machine' - when you've got really nasty confused chop that is impossible to read and is bashing you around the place
'Going up the beat like a ferret up a drainpipe' - a particularly fine piece of nautical terminology coined by the ex-UK olympic coach - basically meaning that you were going up the beat extremely fast!
'tea-bagging' - a particularly unpleasant experience for any trapeze crew, involving your helm deciding to dunk you in the water for no apparent reason.
'cow-boying' - pushing your luck on the race course.
'doing a horizon job' - winning by a vast distance