This is the 7954th most frequent Japanese word.
外道
"外道" (gedō) means "heretic" or "misguided way," often referring to those who deviate from proper teachings or principles.
In this sentence, '外道' is used metaphorically to describe the person's behavior.
彼は外道のように振る舞っているように感じる。
I feel as though he is behaving like a wrongdoer.
Here, '外道' refers to teachings outside of orthodox beliefs.
外道を学んではならない。
One must not study heretical teachings.
The word '外道' here describes wrongful or immoral behavior.