(of air, especially that at high altitudes) containing less oxygen than usual (空气,尤指高海拔的空气)稀薄的;稀疏的 ■(figurative)esoterically distant from the lives and concerns of ordinary people (喻)远离常人生活的;怪异的 debates about the nature of knowledge can seem very rarefied. 有关知识本质的辩论可能会显得深奥难解。