non-Buddhist teachings; tirthika
Buddhist term for teachings or practitioners outside of Buddhism. Often contrasted with 内道 (Buddhist teachings).
See also: 内道
In Buddhism, non-Buddhist teachings are considered not to lead to liberation.
heresy; heterodoxy; unorthodoxy
Extended from the Buddhist sense to mean any belief or practice deviating from the accepted norm. Can refer to a person (heretic) or the doctrine itself.
His theory was treated as heresy in the academic society.
Pejorative term for a person who acts in an inhuman, cruel, or morally repugnant way. Often used as an insult.
I never want to talk to a fiend like that again.
unintended catch; bycatch
Fishing term for a fish species one did not intend to catch. Metaphorically, something unwanted that comes along with the desired thing.
Today was all unintended catches; I didn't catch the fish I was after.
He was called a fiend for that cruel act.
Instead of the fish I was after, I only caught bycatch.
He strayed from the right path and fell into heresy.
鬼畜 literally means 'devil and beast' and is used for someone who commits inhuman acts, while 外道 in this sense is a broader insult for a cruel or repugnant person.
From Buddhist terminology, literally 'outside way', referring to non-Buddhist paths. The pejorative and fishing senses developed metaphorically from the idea of something outside the proper or desired norm.