外患罪 (Gōa-hoān-chōe) (外患罪)，或者 (he̍k-chiá)叛國 (poān-kok) (叛國)，佇 (tī)法律 (hoat-lu̍t)上 (siōng)，指 (chí)一 (chi̍t)个 (ê)人 (lâng)對 (tùi)伊 (i)所 (só͘)屬 (sio̍k)佇的 (ê)國家 (kok-ka)無 (bô)中成 (tiong-sêng); 違背 (ûi-pōe)怹 (in)效忠 (hāu-tiong)宣言 (soan-giân)抑氏 (ia̍h-sī)佮 (kap)怹國家的敵人 (te̍k-jîn)合作 (ha̍p-chok)的人會 (ē)被 (pī)號做 (hō-chò)叛徒 (poān-tô͘) (叛徒)。Oran's Dictionary of the Law (法律辭典 (Sû-tián)) 對外患罪的定義 (tēng-gī)是 (sī): "一个公民 (kong-bîn)協助 (hia̍p-chō͘)外國 (gōa-kok)政府 (chèng-hú)推翻 (thui-hoan)抑是 (ia̍h-sī)嚴重 (giâm-tiōng)侵害 (chhim-hāi)伊所屬佇的國家，或者是使弄 (sái-lōng)外國對伊所屬佇的國家宣戰 (soan-chiàn)."