牙 means 'tusk'

Tusks and fangs may seem unrelated to our lives, but without elephant tusks, we wouldn't have ivory carvings, the color ivory white, a country named Ivory Coast, or the horrible song "Ebony and Ivory." Most of that is also true in Japanese, because 牙 appears in all those terms (excluding the song title). In fact, the Japanese rely on 牙 to an even greater extent; they also use it in expressions about showing hostility, preparing for a fight, and acting in evil ways. On top of that, 牙 is a radical in three Joyo kanji, and it's part of the Shin-Joyo set (the group of characters added to the Joyo set in 2010).