This phrase was made popular by the sales trainer and motivational speaker Brian Tracy.
It means to stare down the most important task of the day and just do it.

My commitment this week is to avoid the (occasional) procrastination that I battle and eat the frog.
What frogs do you need to eat every day?
You can normally identify your frog when you get to the end of the day and say, “Dang… I’ll make sure to do that tomorrow.”
Whatever your ‘that’ is… that’s your frog.
I invite you to join me in dining daily on frogs. 🙂
If you’d like, name your frog in the comments below.