Ev'ry sea dog worth his salt can make use o' the pirate slang words. He who don't know how to use pirate slang words may jus' be a landlubber. The Internet has a bounty of sources that can help. Perfectin' a pirate accent will make your pirate slang words all the more believable. If you're still mocked fer it, make 'em walk th' plank.
Insults are a key part of pirate slang because pirates ain't th' kindest lot. Insults include landlubber, cod piece, bilge rat, bottom-feeder, blow-fish, and swine. Such insults should be preceded by nasty adjectives such as salty, plague-infested, mutinous, hog-faced or rank.
Perhaps more important than the insults are slang words that help ye find yer way about the ship. Most of them are fairly common nautical terms, such as brig for the prisoners and bridge for the main command center.
Some general words include avast for stop, aye for yes, gangway for move, belay for stop and bail to leave. Hearties, or me hearties, is slang for crew mates, to swab is to mop, and the popular ahoy or ahoy there is the pirate's way of saying aloha. Like aloha, it can mean hello or goodbye.
The Cap'n is slang for he who be in charge. A scalawag is a troublemaker, and wench is an insult for a female. If a pirate talks about your dungbie, he's insulting your rear end. You don't want to dance the hempen jig or spend time in hempen halter. The first phrase describes someone hanging, and the second describes the noose.
Two common pirate slang terms have extra meaning. Shiver me timbers is an expression of shock, but it may be derived from the sound of the ship timbers being struck by a cannonball. Jolly Ranger is common slang for a pirate flag, but it really means pretty red in French.