weird damage symbol on weapon

[crasher]

It is the symbol shown in your post we're talking about.
It's not poison though, poison typically does damage over time. This nano effect (the blob symbol showing in your post, which is the same nano effect as the (new) green bio symbol) increases the damage enemies affected by it take from any source by 25%.

I like it.
Turned a regular CS-X into a nano.

[Omnifarious Xji]

The Toxic nano acts exactly like the radiation nano atm.

[Gonjamoon]

The Toxic nano acts exactly like the radiation nano atm.

... but looks and sounds cooler. And when you use it people think that your cool.