Previous discussion of abbreviations/nicknames is here, but I don't advise you read all of it. That way lies derailment, frustration, and possibly a nasty little rash.
But I figured that a glossary would help new people (hi lovely new people, you’re very welcome!) and those of us who find abbreviations difficult to work out, and since pwatson1974 helpfully started one for me, here it is. Square brackets indicate which deck a card is from.
I know this is by no means an exhaustive list, so please feel free to remind me of commonly-used abbreviations/nicknames and I'll add them here. (Note that this is NOT a place for a discussion of whether a glossary is actually needed.)
AA - Argent Adept (hero)
Angry Paul - see IL
AoE - Area of Effect, damaging effects that hit many targets
AZ - Absolute Zero (hero)
Baby Legacy - see YL
BB - Baron Blade (villain)
BGG - Board Game Geek, http://boardgamegeek.com/
CC - Captain Cosmic (hero)
Chrono - Chrono-Ranger (hero)
CR - Chrono-Ranger (hero)
DR - damage reduction
DW - Dark Watch (hero team comprising Expatriette, Mr Fixer, Nightmist and Setback, also refers to the Dark Watch promos for those characters)
EE - Enhanced Edition, the latest version of the base game
Engine Bunker - See EoW
EoD - End of Days [Fanatic]
EoW - Engine of War, Bunker: Engine of War (hero promo variant)
F5 - see FF
FF - Freedom Five (hero team comprising Absolute Zero, Bunker, Legacy, Tachyon and Wraith)
FT - Freedom Tower (environment)
Flip - Reveal the top card of a deck and put it into play, e.g. via Omnitron-X's base power; not to be confused with flipping character cards (especially villains) as described in the rulebook
GH - Grappling Hook [Wraith]
Golem Unity - see GU
GL - Grandpa Legacy, Legacy: Greatest Legacy (hero promo variant)
Grandpa Legacy - see GL
Graveyard - trash, discard pile; not correct Sentinels terminology but often used by Magic: The Gathering players
GSF - Galactic Strike Force, another game by Greater Than Games
GU - Golem Unity, Unity: Golem Spawn (hero promo variant)
GWV - Grand Warlord Voss (villain)
Hairdryer - see Wraith's Hairdyer
IF - Imbued Fire [Ra]
IL - Iron Legacy (villain)
Incapped - Incapacitated
IR - Infernal Relics (expansion)
IREP - Infrared Eyepiece [Wraith]
IT - Isothermic Transducer [Absolute Zero]
Jerk Legacy - see GL
Jim - see CR
KS - Kickstarter
Matty - The Matriarch (villain)
MDP - Mobile Defence Platform [Baron Blade], also Mobile Defence Platform (environment)
Mini-expansion - single decks sold individually (i.e. not part of the base set or a regular expansion), currently comprising The Scholar, Unity, Ambuscade, Miss Information, Silver Gulch 1883 and The Final Wasteland
Mister Chomps - Raptor Bot [Unity]
MTC - Micro-Targeting Computer [Wraith]
NPCU - Null-Point Calibration Unit [Absolute Zero]
Omni-10 - see OX
Omniton-10 - see OX
Omnitronks - see OX
Omnix - see OX
OX - Omnitron-X (hero)
Plink - Deal exactly 1 damage
PR - See Rat
Promo - alternative character card with different base power and/or hit points to be used with the original deck, e.g. America's Newest Legacy
PtL - Pushing the Limits [Tachyon]
PW - Prime Wardens (hero team comprising the Argent Adept, Captain Cosmic, Fanatic, Haka and Tempest, also refers to the Prime Wardens promos for those characters)
Rat, the - Plague Rat (villain)
RC - Rook City (expansion and environment)
Soak - damage reduction
SDS - Self-Destruct Sequence [Wagner Mars Base]
SHD - Super-Human Durability [Legacy]
SotM - Sentinels of the Multiverse
ST - Shattered Timelines (expansion)
Tactics - Sentinel Tactics, another game by Greater Than Games, scheduled to be released in December 2014
TLT - Team Leader Tachyon, Tachyon: Team Leader (hero promo variant)
That Card - Devastating Aurora [Citizen Dawn]
TtE - Twist the Ether [Visionary]
Wraith's Hairdryer - Impromptu Invention [Wraith]
WotC - Wrath of the Cosmos (expansion)
WtM - Wrest the Mind [Visionary]
Young Legacy - see YL
YL - Young Legacy, Legacy: America's Newest Legacy (hero promo variant)
