?亡佚
亡羊补牢 better late than never; to lock the stable door after the horse has bolted 亡佚 nonextant; lost to the ages 无神论者 atheist ..
nonextant:
non- +? extant
英汉双解词典包含3185865条英汉词条，基本涵盖了全部常用单词的翻译及用法，是英语学习的有利工具。