Addled -- Mad, insane, or just stupid. An "addlepate" is a fool.
Avast! -- "Hey!" Could be used as "Stop that!" or "Who goes there?"
Begad! -- By God!
Belay -- Stop that. "Belay that talk!" would mean "Shut up!"
Blimey! -- An exclamation of surprise.
Booty -- Loot.
Cap'n -- Short for "captain."
Cat o'nine tails, or just "cat" -- a whip with many lashes, used for flogging. "A taste of the cat" might refer to a full flogging, or just a single blow to "smarten up" a recalcitrant hand.
Fair winds! -- Goodbye, good luck!.
Grog -- Generically, any alcoholic drink. Specifically, rum diluted with water to make it go farther.
Grub -- Food.
Handsomely -- Quickly. "Handsomely now, men!" = "Hurry up!"
Matey -- A piratical way to address someone in a cheerful, if not necessarily friendly, fashion.
No quarter! -- Surrender will not be accepted.
On the Account -- The piratical life. A man who went "on the account" was turning pirate.
Rum (noun) -- Traditional pirate drink.
Rum (adjective) -- Strange or odd. A "rum fellow" is a peculiar person, the sort who won't say "Arrrr!" on Talk Like A Pirate Day.
Wench -- An individual of the female persuasion. "Saucy" is a good adjective to add to this, and if ye can get away with "Me proud beauty!," more power to ye.
Yo-ho-ho -- A very piratical thing to say, whether it actually means anything or not.