noun
Buddhist nun
Specifically a female Buddhist monastic; the male equivalent is 僧 (そう).
彼女は若くして尼になり、寺で修行を積んだ。
She became a Buddhist nun at a young age and trained at a temple.
noun
Catholic nun; sister
Used for Christian nuns; context distinguishes from the Buddhist sense.
修道院で尼たちが祈りを捧げていた。
The nuns were offering prayers at the convent.
noun
Derogatory and dated; usually written in katakana as アマ. Strongly offensive.
あのアマ、また嘘をついたのか。
That bitch lied again, didn't she?
noun
Amagasaki
Slang abbreviation of 尼崎 (Amagasaki), a city in Hyogo Prefecture. Often written in katakana.
週末にアマで飲み会がある。
There's a drinking party in Amagasaki this weekend.
noun
Internet slang for the online retailer Amazon. Typically written in katakana.
その本、アマで注文したよ。
I ordered that book on Amazon.
From Sanskrit amba (mother) via Chinese, originally a respectful term for a female ascetic. The derogatory sense likely developed as a pejorative extension, and the slang abbreviations are modern shortenings.