unprecedented
词形变化：
同义词：
extraordinary | exceptional | unduplicated | unique | amazing | signal | original | unparalleled | record | first-time | unmatched |
反义词：
词义辨析：
同义:
a.无先例的, 空前的
unduplicated
extraordinary
exceptional
同义参见:
signal
amazing
unique
original
反义:
a.无先例的, 空前的
precedented