Definition - What does Turtling mean?
Turtling is a gaming strategy where the player focuses on building up his defenses rather than going on the attack. It is most commonly used to refer to a common technique in real-time strategy games where a player builds up as many defenses and units as possible to withstand attacks and eventually win a war of attrition over opponents. Turtling has also been used in a derogatory sense to refer to gamers who play fighting and first-person shooter (FPS) games in a way that depends heavily on defense, such as blocking, counter-attacking and then avoiding attacks until the time runs out.
A person who engages in turtling is called a turtle.
Techopedia explains Turtling
Turtling is a relatively straightforward strategy that calls up the image of a turtle hiding in its shell. By building up formidable defenses or clustering units around the home base (or both), a player can often fend off assaults. This is because the game's artificial intelligence and the game's other players often split forces into two (or more) groups – one charged with defending and the other with attacking the opponent. As a result, numbers are almost always on the side of the turtling team, assuming that it is creating units at the same pace.
However, in the interest of keeping the gameplay balanced (and exciting), many game designers have ways to punish turtling. By ranging, players may find large-scale weapons that can kill multiple units, or items that help build their own units faster. That said, some players combine turtling with a "zerg" strategy, in which they attack once they have generated overwhelming numbers.
Turtling, while perhaps fun for the player doing it, is not considered sportsmanlike because counter-turtling is either a waste of time (not fun) or depends on an in-game punishment like a super-bomb to gain victory (a cheap win).