Like many Japanese young people my son is into Japan's ubiquitous BBS 2ch (pronounced ni-channeru in Japanese), where all manner of anonymous Japanese net users post news, debate issues and sometimes make rants that are amusing to read. As he reads the matome (thread summary) sites, he knows it should always be on the lookout for good neta for me. This is a Japanese word with many definitions, first and foremost referring to the top part of a piece of sushi (the fish part that sits on top of the rice, which is called shari if you were curious). The word neta has other meanings, too, including material for a joke, or in my own case, ideas for these little missives I write here. The word for "spoiler" in Japanese is netabare (neta-bah-ray, lit. to expose an idea to everyone), and whenever Hollywood tries to make a motion picture based on an anime, fans accuse them of being netagire (neta-gi-reh, meaning "completely out of ideas"). And the word for "NSFW" (not safe for work, meaning material that might be too ecchi for some situations) is shimoneta, basically "ideas related to the lower half of your body." Now you know some random Japanese words.
Now you know how to say "spoilers" in Japanese.