What is an Adverse Action in the US Army?

Adverse Actions are things like loss of rank, pay ,extra duty or loss of passes. They can also include things like bar of re-enlistments and being flagged.

They can be given for things like coming up hot on a piss test, missing movement, being late multiple times, failing a PT test or height and weight (more than once), disrespecting officers or NCO's just as some examples.

They aren't sabotage (as qwerty has tried to tell you in his post) it's corrective punishment and in order to do one there has to be a pretty lengthy paper trail to go along with it. They are just handed out at a whim and are not taken lightly, If a Soldier is getting counseling statements and corrective training but still screwing off then they go to the next step which is usually an ART 15 for the infraction. That will usually result i(depending on type of ART 15 given) with extra duty, loss of pay and rank.

Adverse Action Definition

there are many adverse action ranging from minor to sabotage if they are minor and you have a clean record then you may have to serve a minor penalty, look in wikipedia there is a lot of info there.