abunai (危ない) means ‘dangerous!’ ABUNAI kanji fall into 3 types:
Note that there's not a lot of kanji that are offensive by themselves (although there are plenty of kanji with politically incorrect roots, which might be offensive or funny to gaijin).
But, when you combine two or more kanji together, you can make plenty of JUKUGO (compound words) that will offend people!
If you know the individual kanji, it's easy to recognize clearly offensive jukugo, even if you have never seen them before - 陰唇 (inshin) literally means 'shadow lips' or 'hidden lips' and 巨根 (kyokon) literally means 'giant root.' Take a wild guess, Einstein.
But, Japan being Japan, a lot of offensive or embarrassing terms are even more subtle. For instance, 事務所 (literally, 'office') is usually just that: an office. But often it's used to mean Yakuza, since mobsters here are as official and well-organized as big businesses. Welcome to Japanese sarcasm.
Another example: 犯す (okasu). According to your dictionary, this means, 'to perpetrate.' What your dictionary DOESN'T tell you is that 犯す is almost always used in the context of rape. (also, it doesn't help that it sounds almost exactly like 'wake me up' (起こす, pronounced oKOsu), which has resulted in more than one embarrassing incident for me, but probably you don't have that problem).
Fortunately, Kanji Damage has a solution for you: offensive or dangerous kanji/jukugo are tagged with the label ABU (short for abunai 危ない, which means 'Danger!'). And, in the cases of words like 事務所 or 犯す, I will explain specifically why they might get you into trouble.