Here are some terms/abbreviations in no particular order:
TCG: Trading Card Game
Donk: Your active Pokemon gets a knock out on the first turn on the Defending Pokemon and they have no Pokemon left on the bench. (Getting Donk-ed or Getting a Donk.)
Active Pokemon: The Pokemon you are using to attack or take damage.
Defending Pokemon: The opponent's Active Pokemon.
DCE: Double Colorless Energy.
Format: A particular set period of time when cards from particular sets are legal for tournament play.
Sniping: When a Pokemon's attack deals damage to particular benched Pokemon.
Mulligan: When you draw 7 cards and draw no basic Pokemon in your opening hand.
Opening Hand: The first 7 cards you draw to start the game !
Unlimited Format: When you can play ALL cards printed in a particular deck.
Modified Format: When certain sets are restricted from play due to rotation or through an agreement with said players choice.
Examples: "No Base Set cards allowed"
"Black and White on wards format"
Tournament Format: The sets which are allowed to be used in tournaments due to rotations.
Wiff/Wiffing: A term used to describe when you play a card and it does not go your way.
Examples: "I got a tails on a crushing hammer and I needed that to by time and prevent my opponent from attacking !"
"I got tails on a Super Scoop up ! Now I'm stuck with this Pokemon in my Active position"
"I played a Professor Juniper to draw a fresh hand of 7 cards, but I did not draw the Double Colorless energy I needed for my Mewtwo EX to attack that turn !"
Catcher/Catchered: Short for the use of a "Pokemon Catcher."
Example: "I drew a catcher and decided to catcher out his Mewtwo EX for the revenge KO !"
KO: Knock Out
OHKO: One Hit Knock Out
Revenge: To knock out an opponent's Pokemon after you lost a Pokemon to a Knock out yourself.
Deck out: When you or your opponent have no cards left to draw from your deck.
Examples: "I decked out my opponent using Devour with Durrant!"
Basic: Short for "Basic Pokemon."
Scrub: A term which is very general to describe "a bad player" or not making the top cut of a tournament(s).
Rotation: When particular sets become no longer tournament legal.
Jank: An opinionated term used to describe card(s) that are considered worthless and not worthy of current tournament play.
X-X-X: Pokemon line ups used to describe basic, stage 1 and stage 2 evolution line.
Example: "I run a 4-2-4 of Charizard. So 4 Charmander, 2 Charmeleon, 4 Charizard"
"I run a 2-2 Blissy line. So 2 Chansey and 2 Blissy"
Tech: A single copy of a card which is down to the personal preference of the player.
"I run a tech copy of 'Tool Scrapper' as I can search it out with Skyla if I need it."
Top deck: A term used to describe when a player is drawing the card(s) he needs.
Example:"I only had 1 card in hand and then I top decked the Professor Juniper ! Yes ! A fresh hand of 7 cards !"
"I top decked the Pokemon Catcher to catcher out his damaged EX to take my last 2 prizes for game !"
Meta or Meta-game: A term used to describe what cards are recently being played in current tournaments.
Net-decking: A term used to describe copying and building a deck exactly card for card from a deck list source.
Damage Counter: A damage counter represents 10 damage in Pokemon TCG.
Example: Put 2 damage counters on the defending Pokemon (put 20 damage on the defending Pokemon.)
Pulling: A term used to describe when you open a booster pack.
"I just pulled a Mewtwo EX from a next destinies pack !"
Sneak Peak: Also known as a Pre-release.
Pre-release: An event organised by Play Pokemon which allows you to open booster packs and play a special event which involves using cards from the latest set to be released.
POP: Pokemon Organised Play
Mill or Milling: A term which originated from MTG (Magic the Gathering) of sending cards from your opponents deck or your deck to the graveyard.
Example: "I had 4 Durant in play and used the attack 'Devour' to mill 4 cards from my opponent's deck to the discard pile."
Counter: A card which can be used to deal with a threat, strategically - i.e for deck building purposes.
Example: In general Terrakion NVI counters Darkrai EX.
Out: A card which can be used to deal with a threat, tactically - i.e when you are playing against someone, so dependent on the situation.
Example: Terrakion is an out to Darkrai EX but if Darkrai EX holds Eviolite, then Terrakion EX is no longer an out.
Check: A card which makes an opponent unwilling to commit another card to the field.
Example: Landorus EX would make an opponent unwilling to bench Dark Deino.
Failed search: When someone plays a search card and does not search anything out. Can be done with or without intention.
"Power through ambition." - Overlord Drakow Forum Set // Pair