"Opornik" is a colloquial word from CS2 players' vocabulary. It has no single "official" definition: the term appears neither in the game's menus nor in tournament rules, and instead lives in voice chat, on streams, and in community discussions. Its meaning therefore depends on context, and it is important to understand what exactly is meant.
What people usually mean
In most cases, "opornik" refers to a massive map element that carries part of the level's structure: a column, a concrete wall, an overhead slab, a thick crate. A player can take cover from fire behind such a structure, and sometimes, conversely, it serves as a landmark when defending a position. The phrase "sit behind the opornik" means "hide behind the load-bearing wall or large object."
A second topic has also become attached to the word: wallbanging. Wallbanging means shooting through a thin obstacle (a wooden door, a crate, a light partition). In CS2, bullets really do pass through some materials, losing part of their damage. Players discuss which objects can be shot through and which cannot. In such conversations, an opornik is precisely "something thick and reliable": shooting through it is pointless, and you can feel safe behind it. How a bullet passes through a specific object depends on the material and thickness, and you can check this in the game itself on a practice map.
An example from the game
Suppose a defender is standing at a position next to a massive concrete column. The opponent knows the column cannot be shot through, so instead of wasting ammo "spamming" through it, they prepare an entry from another side. The defender, in turn, uses the column as support: peeking out, shooting, and returning to cover. This is the typical usage of the word.
Opornik and cheats
The word sometimes surfaces in dubious contexts: in videos and ads for "guides" that promise a "perfect wallbang through the opornik" without any practice. Caution is warranted here. Exact wallbang spots and timings are indeed the subject of honest breakdowns: they are studied, practiced on a practice map, and discussed on streams. But a promise of a flawless result after a couple of minutes of watching is a sign of either exaggeration or the sale of third-party software. Using cheats is prohibited by the game's rules and leads to an account ban, while honest map knowledge is built on practice, not on a magic button.
Where the word comes from
The term derives from the ordinary construction phrase "support structure" (опорная конструкция) and crossed over into slang by analogy with other map-related words: "angles," "peek," "wallbang." It has no special history, and different groups of players probably put slightly different meanings into it. If you hear the word in an unfamiliar situation, the easiest thing to do is ask which specific object on the map is meant.