To decimate something such as a group of people or animals means to destroy a very large number of them.
例句
The pollution could decimate the river's thriving population of kingfishers...污染可能會造成河邊大量繁殖的翠鳥大批死亡。British forces in the Caribbean were being decimated by disease.加勒比海地區的英國部隊有大批的人病死。
VERB
嚴重削弱，大幅縮減(系統或機構)
To decimate a system or organization means to reduce its size and effectiveness greatly.
例句
...a recession which decimated the nation's manufacturing industry.使該國制造業元氣大傷的經濟衰退
英英詞典釋義
Noun
1. destroying or killing a large part of the population (literally every tenth person as chosen by lot)