Liar
noun, の adjective
If lies puke (吐く) out of your mouth, you're a liar.
This is a combination of the kun'yomi readings, one of which you haven't seen yet. You'll usually see this word without the 吐 kanji, as in 嘘つき, but for now let's learn its kanji reading!
You can't just tell one lie, it always turns into two (つ). Kind of like a chip or pretzel, you can't just have one. With lies, you have to open your mouth for two more. And then two more.... and... well you get it.
ウソップは嘘吐きだ。
Usopp is a liar.
フグ子ちゃん、大嘘つきの彼氏がいて、よくケンカするんだって。
Apparently, Fuguko has a boyfriend who is a complete liar and they fight quite often.
その時代、嘘吐きは全員燃やされていた。
In that era, all liars were to be burned.