No gamer
A No-Gamer, or No games, is a /tg/ slang used as insult towards those who, if the term was not of any indication, do not play games. That's it.
Well, there's a bit more to it than that, but given how much this sort of remark is a low-blow, even by /tg/'s standards, you really shouldn't put more thought into it. Which is why we did that for you!
If we want to be real with you, this insult is thrown around like Commissars shooting their own men; all the goddamn time. So much so that sometimes, it might feel like this insult is mostly aimless. No-gamers are, debatably, a real thing. But to assume that everyone who disagree with anon over there is a no-gamer, it's just a tiny bit ridiculous. Should you find yourself called like that, take it with a grain of salt, unless you really do not play games.
Definition
A "No games" is a person who is familiar with /tg/-related tabletop games but who does not play them. However, in spite of his lack of actual experience in the game, he will still partake in discussions surrounding the game and think that his opinions hold up to that of someone who is, let's say, a veteran. Most of the subjects they talk about usually involves fluff, or things like story-telling or products related to the TT game, such as video-games.
If you felt targeted by that particular description, don't you worry. Especially if you don't pretend that your word is worth something than that to someone who plays the game frequently. "No games" can include absolutely anyone who isn't involved directly into the game.
To explain why this insult even came to be, we have to understand the general state of /tg/. A lot of users have been complaining for the decline of the board, especially regarding the content generated. A lot of game-related discussions are contained inside generals, in a similar manner to /vg/, and other threads tend to focus around various subjects somewhat related to TTRPGs or Wargames. A lot of them tend to discuss worldubuilding, situations happening during sessions, various opinions on settings and game-design, or time-wasting questions about everything and nothing. Plenty loathe this sort of content being generated, and often create strawmen to blame the lack of quality threads being posted. Some call out specific people, some usually blame the mentality of a ubiquitous userbase of "newfags".
This sheer hate for these threads mostly comes in a lack of productivity coming from the whole board, where community projects and homebrews aren't as bountiful as they used to be. Some could argue this is due to the fact that the TTRPG scene is becoming increasingly more mainstream, and thus a lot of old veterans employ extreme gatekeeping and elitism to simulate an ideal of discussion on the board.
A lot of hate is actually targeted towards those interested in the lore and worldbuilding of any setting discussed on /tg/. Some threads are even centered around writing entire worlds without ever having the intent of making a game around them. This is probably due to the fact that /tg/ is the only board that engages in discussion surrounding the structure and inner-logic of fantasy worlds, whereas other boards like /v/, /tv/ or /lit/ are more likely to frown upon this practice, them being more interesting in gameplay, execution or writing respectively. That, and Tabletop games share a particular relationship with fantasy and sci-fi. So until there's a worldbuilding board, most Tolkien-in-the-making are bound to post on /tg/.
So of course, "no games" became an insult for them. Mostly because a lot of their discussion centered around very fluffy details of their worlds that wouldn't exactly matter in the context of an RPG session. This, of course, ended with the insult becoming largely overused, usually to discredit everyone and everything who dares being an argument into a conversation.