i-adjective
Colloquial, often used in casual speech to express fear or unease. Common in eastern Japan dialects but widely understood.
あの先生はおっかない顔をしている。
That teacher has a scary face.
夜
Walking alone at night is frightening.
i-adjective
Archaic use meaning 'extreme' or 'exaggerated'; not used in modern Japanese outside of historical or dialectal contexts.
昔の言葉で「おっかない」は「途方もない」という意味でも使われた。
In old language, おっかない was also used to mean 'outrageous' or 'extreme'.