I once heard an executive describe a decision as a "no brainer." He meant that the action he'd taken was such an obvious one that no serious thought was required.
There were several reasons why some additional brain power would have helped. Still, my opinion wasn't solicited at that time so I held an uncharacteristic silence and instead raised an eyebrow.
[My eyebrows are eloquent.]
He then asked for my opinion and so I outlined the ways in which the decision could blow up.
I didn't persuade him.
That was fine. His decision was not a poor one and could even have been sound.
But I do know one thing for certain; it was not a "no brainer."