What in the world is a showbox?

So I’m proofing a manuscript today and Word has the word showbox underlined with a red squiggle. For the life of me I had no idea what a showbox was. I read the sentence, then the surrounding paragraph. Nope. No clue what I meant. Read it one more time and the light bulb went off.

Shoebox. I guess I was going for shoe box.

These are the random goofups that occur when I’m tired, writing on my phone or using my waterproof keyboard in the bathtub. I really should get a new keyboard; the A key no longer works on that one.