Multiplayer

Gamers know it refers to: Any game mode that can be played with one or more other players, either co-operat♒ively, competitively, simultaneously or by way of a turn system.

Non-gamers think it means: A CD changer

Battery back-up

Gamers know it refers to: Th⛄e use of powered writable memory built into game cartridges to save game dat🗹a.

Non-gamers think it means: Carrying a spare ba𝔍ttery around in case your MP3 player packs up on a long train journ✃ey.

Level grinding

Gamers know it refers to: Repeated execution of🅷 lower-level side-quests or combat in an RPG in order to attritionally increase an avatars experience level and abilities.

Non-gamers think it means: Really smooth masonry work.

CoD

Gamers know it refers to: Any given entry in the Call of Duty franchise, or the entire💃 franchise as a whole

Non-gamers think it means: Fish.

Character model

Gamers know it refers to: A sculpted and textured polygon mesh꧒ used to build an in-game protagonist, enemy or NPC.

Non-gamers think it means: The poor bastards who go through years of theatrical and modelling training only to end up pos🐠ing in a pirate costume for a fancy dress web-site's promotional photographs.

Kill-screen

Gamers know it refers to: The c🐲rashed video display resulting from a fatal game glitch, more common during the golden gaming age of the 70s and 80s when unaccomodated high scores in particular would break a games internal mathematical system.

Non-gamers think it means: The crescendo of a particularly gory scene in a horro𒊎r film.

Sky box

Gamers know it refers to: The textured enclosure used by 3D games to simulate th𝓰🌊e sky in outdoor areas.

Non-gamers think it means: The thing that si🐻ts underneath the TV and decodes satellite televi📖sion broadcasts.

XP system

Gamers know it refers to: An underlyi🍨ng character ability development system using a currency🔯 of experience points imparted in exchange for in-game actions.

Non-gamers think it means: A PC running a 10-year-old version of Windows.

Sprite

Gamers know it refers to: A piece of 2D art used to𝓰 depict an in-game character, object or special effect.

Non-gamers think it means: A small supernatural creature, usually humanoid and often having some ඣsort of elemental properties.

Super combo

Gamers know it refers to: An unblockable string of attacks in a fighting ga💫me, comprising or culminating in the execution of a special powered-up attack which i♈s earned by charging a dedicated power bar.

Non-gamers think it means: A really good band.