What does "pairwise" mean in graph theory? if someone says "a graph with 8 pairwise adjacent vertices" is that only 1 possible graph or is it something that could be drawn many different ways?  I know that adjacent vertices are vertices connected by an edge, but I'm not entirely sure what "pairwise" means and about an hour of googling didn't help.
For example if I have these graphs:
https://imgur.com/a/wefnqe9
are they all "graphs with 8 pairwise adjacent vertices"?
ADDITION:
so is this asking for a complete graph with 8 vertices like this: https://upload.wikimedia.org/wikipedia/commons/thumb/c/cb/7-simplex_graph.svg/1024px-7-simplex_graph.svg.png ?
Please just draw me a picture
 A: Take the statement "A graph has n vertices that are pairwise X", where X can be anything. In your example, X is 'adjacent'. The term "pairwise" means that every possible pair of those n vertices satisfies X.
Applying this to your example, it means that each pair of those 8 vertices are adjacent. You correctly concluded that the result is a complete graph on 8 vertices.
A: 
if someone says "a graph with 8 pairwise adjacent vertices" is that only 1 possible graph 

Depends what a "graph" is in your context. If we are talking about simple graphs, there is only one, the complete graph $K_8$ on eight vertices, which you already linked from Wikimedia Commons. If you allow parallel edges though, there are infinitely many such graphs, as you can replace the edge connecting any two adjacent vertices by as many as you like.
Although most of the time people speak about simple graphs.
So when you speak about "pairwise vertices" from the vertex set $V$ having some property $\mathcal P$, this usually translates to $$\forall u,v\in V:u\neq v\Rightarrow\mathcal P(u,v),$$ because $\{u,v\}\subseteq V$ with $u\neq v$ constitutes a(n unordered) pair. Sometimes the $u\neq v$ condition is dropped and the statement simply becomes $$\forall u,v\in V:\mathcal P(u,v),$$ because $(u,v)$ constitutes a(n ordered) pair. This is usually clear from context. In your example, since $P(u,v)=$ "$u$ and $v$ are adjacent" is a symmetric property (i.e. $P(u,v)\iff P(v,u)$), the unordered pair would be the safe bet here.

or is it something that could be drawn many different ways?

That is a different question, because the same graph can be drawn in different ways. Here is an alternative drawing of $K_8$: 
It is still the same graph as the one you found on Wikimedia commons.

For example if I have these graphs: https://imgur.com/a/wefnqe9 are they all "graphs with 8 pairwise adjacent vertices"?

No. In each of these pictures you can take the vertex most on the left (let's call it $u$) and the vertex most on the right ($v$) and they are not adjacent, so not all 8 vertices are pairwise adjacent, because $\{u,v\}$ are a pair that are not adjacent.
