What is the meaning of the word "lockstep"?

Definitions:

  1. a manner of marching in file in which each person's leg moves with and behind the corresponding leg of the person ahead copy to clipboard noun
    • the prisoner's ankles were so chained together that they could only march in lockstep copy to clipboard
  2. a standard procedure that is followed mindlessly copy to clipboard noun
    • the union's support had been in lockstep for years copy to clipboard