[v] make chemically neutral; "She neutralized the solution"
[v] make ineffective by counterbalancing the effect of; "Her optimism neutralizes his gloom"; "This action will negate the effect of my efforts"
[v] make incapable of military action
[v] make politically neutral and thus inoffensive
[v] oppose and mitigate the effects of by contrary actions; "This will counteract the foolish actions of my colleagues"