Definition of "lemming"

The well-known lemmings, in severe winters, at long intervals, move down from the mountains of Scandinavia in immense numbers, crossing lakes and rivers, eating their way through haystacks, and surmounting every obstacle till they reach the sea, whence very few return.

1876, Alfred Russel Wallace, The Geographical Distribution of Animals, chapter 2, page 18

Like a lemming, I followed the crowd, got to the right line and was concentrating hard when queried by the customs officer.

2014, M.P. Fedunkiw, A Degree of Futility‎, page 61

Lemmings are strongly cohesive, but could be, in organisational terms, highly destructive for the business.

2004, Ilse Hobbs, Jan Havenga, A Practical Guide to Strategy, page 127