How do you define when you've "completed" a game?

when i don't care to play it anymore or its "play me magic" doesn't make me

there's some seriously fucked up games though - skyrim being one ... what the shit is it? a game with unsatisfying combat,
a good looking screensaver to simulate outdoor activity, a demo to try out nude-mods ... don't know and i'll never find out

It's usually 100% achievements for me. I could get bored or annoyed by a game before reaching that though. Or I could deem it as impossible for me (for example I'm pretty sure I don't have the reflexes needed to beat most Bullet Hell games on their final difficulty).

beaten : done the story
completed : all achiev

despite the poll, it seems most comments agree on completed (100%) vs beaten/finished

Differs per game, games that don't have an achievement and you just reach a the end or game over.
Games that have reasonable achievements and getting them all.
Games that don't have reasonable achievements but you get tired of it.
Some games simply have no ending.

some games achievements are ridicolously stupid and is nothing more than work, grind work. if i finished the main story its finished but some games offer fun side quests and i will do them too. It really depends on the game. open sandbox games with no real end can be played for hundreds of hours and there are AAA-title with a story who end after 6-20 hours.

My own definitions are as followed:

-Completed a game: Got all achievements and did everything reasonable in the game (ie not bothering to get pointless collectibles which don't count towards anything, such as the 'loot crates' in Far Cry 3).

-Beat a game: Gotten through main story, primarily exists for single player stories or campaigns.

-Finished/Done with a game: Played the game enough that there is no more enjoyment or fun for me to really have in the game. (For instance, got 49/50 achievements for Spec Ops: The Line, but not going for the last one for beating game on FUBAR difficulty despite enjoying the game a lot, because some sections have your survivability to the next checkpoint based entirely on bullet RNG. Playing a 20 second linear running-from-helicopter section in which you're estimated to spend 10 hours trying to beat isn't fun, especially with long loading time between the runs). The point of a game to me is fun and enjoyment, if it's not fun then there is little point to it.

"Completing" means 100%ing the game.
Other completion % can be "beating"/"finishing"/"being done" with the game.
Depending on the game, is when I'm done with it, i.e. concluded all I'm going to do inside it.

Singleplayer: Absolutely everything is completed, I've done every side quest, gotten every collectable and ending and gained every achievement. When I know with 100% certainty, do I consider it done (then they always release a DLC after THE MONSTERS)

Multiplayer: Bit more situational. I tend to focus on where I'm ranked than on achievements. Focusing on getting rlly tedious achievements is gonna make the game boring and frustrating. So I'll just get my 100 combo achievo by trying to hit rank 1 thanks

completed as in blaeo's definition?
100%, but i rarely go for that, especially with multiplayer games or difficulty-based achievements.

i'd rather go with "beaten", which is usually completing the main quest unless it's endless or sandbox, so i try to see what's everything i could do and go for it (like finishing all 3 planetary offenses in helldivers).
i also like to unlock some achievements if they are easy and don't affect my current run of the game (save > unlock it > reload the game, like in dishonored).
a bit offtopic, but i hate to rush/speedrun games. i feel it's a waste of a good game i wanted to play/win and it's also pretty rude when the ga creator looks at the playtime and sees a 15 hours game beaten in 10 with minimal effort.

In most game , when I pass main plot , i think it's completed.
If this game get all achievements cost me 40 hr or less ,I'll try to get all achievements