"Pissed off" means angry to us. "Pissed" alone means drunk.
Incidentally, we have over 140 euphemisms for "drunk". (Below are a few - I've missed out the more offensive ones). Peapod will say that we Brits drink too much, but that allegation is unfounded.
Ankled
Badgered, Banjaxed, Battered, Befuggered, Bernard Langered, Bladdered, Blasted, Blathered, Bleezin, Blitzed, Blootered, Blottoed, Bluttered, Boogaloo, Brahms & Liszt, Buckled, Burlin
Cabbaged, Chevy Chased, Clobbered
Decimated, Dot Cottoned, Druck-steaming, Drunk as a Lord, Drunk as a skunk
Etched
Fecked, Fleemered, Four to the floor
Gatted, Goosed, Got my beer goggles on, Guttered
Had a couple of shickers, Hammer-blowed, Hammered, Hanging, Having the whirlygigs, Howling
Inebriated, Intoxicated
Jahalered, Jaiked up, Jan'd - abbrev for Jan Hammered, Jaxied, Jeremied, Jolly
Kaned
Lagged up, Lamped, Langered [also langers, langerated], Laroped, or alt. larrupt, Lashed, Leathered, Legless, Liquored up (South Carolina), Locked, Locked out of your mind, Loo la
Mad wey it, Mandoo-ed, Mangled, Manky, Mashed, Meff'd, Merl Haggard, Merry, Minced, Ming-ho, Minging, Moired, Monged, Monkey-full, Mottled, Mullered
Newcastled, Nicely irrigated with horizontal lubricant
Off me pickle, Off me trolley, On a campaign, Out of it, Out yer tree
Paggered, Palintoshed, Paraletic, Peelywally, Peevied, Pickled, Pie-eyed, Pished, Plastered, Poleaxed, Pollatic
Rat-legged (Stockport), Ratted, Ravaged, Razzled, Reek-ho, Rendered, Rosy glow, Rubbered, Ruined, Rat-arsed
Saying hello to Mr Armitage, Scattered, Schindlers, Screwed, Scuttered, Shedded [as in " My shed has collapsed taking most of the fence with it"], Slaughtered, Sloshed, Smashed, Snatered (Ireland), Snobbled (Wales), Sozzled, Spangled, Spannered, Spiffed, Spongelled, Squiffy, Steamin, Steampigged, Stocious, Stonkin
Tanked, Tashered, Tipsy, Trashed, Trollied, Troubled, Trousered, Twisted
Warped, Wasted, Wellied, With the fairies, Wrecked
Zombied