To decimate means to destroy or kill a large portion of something, often dramatically reducing its numbers or strength. When a forest fire decimates a wildlife population, it wipes out a huge number of animals. When a disease decimates a crop, farmers lose most of their harvest.

You might read that a hurricane decimated a coastal town, meaning it caused widespread destruction. A harsh winter might decimate a bee colony. A scandal might decimate a politician's support. In each case, the damage is serious and extensive, though it’s rarely precisely measured.

In modern English, decimate describes any devastating loss or destruction that leaves something severely weakened. When you see decimated in a news article or book, think of something that's been hit hard and had much of it destroyed.