The phrase "safest thing" means the option or action that is least likely to cause harm or danger. It refers to making choices that provide the highest level of safety and protection. Full definition
With all the changes that have happened to your body over the last 9 months doing what you did before getting pregnant might not be the smartest and safest thing for your body. (intuitivehandspt.com)
I don't want people to be worried about the consequences of decisions and only do safe things that don't propel us forward as an enterprise. (luigibenetton.com)
Make sure he has lots of safe things around to touch, mouth, and manipulate. (babycenter.com)