(~s)
1.
A ~ is an animal that looks like a large rat with thick fur. Lemmings live in cold northern regions and sometimes travel in very large numbers.
N-COUNT
2.
If you say that a large group of people are acting like ~s, you are critical of them because they all follow each other into an action without thinking about it.
The French crowds pour like ~s down the motorway to Paris.
N-COUNT: usu pl disapproval