Disagree and commit is a management principle which states that individuals are allowed to disagree while a decision is being made, but that once a decision has been made, everybody must commit to it1.
Sounds good in theory. I can see it working If the individuals involved are at the same level in the hierarchy or the individual disagreeing and committing has more power than the individual proposing an idea.
In my experience, it falls apart when the person disagreeing has less power than the person proposing an idea. The person with the most power ends up using disagree and commit as an excuse to force the other person into a corner where disagreeing is seen as not being a good teammate.