lemmings

noun
  1. 1

    A small Arctic and Subarctic rodent from any of six genera of similar rodents.

  2. 2

    Any member of a group given to conformity or groupthink, especially a group poised to follow a leader off a cliff.

Source: https://en.wiktionary.org/wiki/lemming, https://en.wiktionary.org/wiki/lemmings