動詞 toss 的意思是扔，擲。如果某個形勢被形容為 a toss-up, 那麼就意味著兩種不同結果發生的機率是一樣的。
It's a toss-up between pancakes and risotto tonight. I'm not sure what to cook yet.
We haven't recruited a presenter yet, but it's a toss-up between Sarah and Julie.
My boyfriend doesn't know what he wants for his birthday yet. It's a toss-up between a new mobile phone and an e-reader.
短語 toss up 的由來是以前人們把硬幣拋向空中，然後猜一猜是正面 heads 還是背面 tails 朝上。人們往往用這種方式來決定作出哪種選擇來解決問題。比如:
My friend wanted to go to the cinema but I really wanted to go ice-skating instead. We tossed a coin to decide: I chose 'heads' and won!
Neither of them wanted to do the washing up, so they tossed a coin. They decided if it landed on 'heads' she would have to do it, and if it landed on 'tails' he would.