yak butter(n = noun.food) - butter made from yaks' milk;
is a kind of butter

anchovy butter, apple butter, bercy butter, bread and butter, bread and butter pickle, brown butter, butter, butter and eggs, butter bean, butter churn, butter cookie, butter daisy, butter dish, butter knife, butter up, clarified butter, cocoa butter, colbert butter, drawn butter, garlic butter, lemon butter, lobster butter, meuniere butter, nut butter, onion butter, peanut butter, pimento butter, shrimp butter, snail butter, witches' butter, yak