What term describes a manager who makes himself visible, being present for employees, and getting out of his office to interact with employees?

An open door policy means a manager makes themselves available for employees who choose to come to them - it does not describe the manager proactively going out to find and interact with employees.

Progressive discipline is a structured, escalating system of corrective actions used to address employee misconduct or performance deficiencies - it has no connection to manager visibility or physical presence.

'Active management' is not a recognized or standard management term for this specific leadership practice - it is too generic and does not capture the defining characteristic of a manager walking the floor to engage employees.

Management by Walking Around (MBWA) is a concept popularized by Tom Peters and Robert Waterman in 'In Search of Excellence' (1982) and closely associated with Hewlett-Packard's management culture. It specifically refers to managers physically moving through the workplace to observe, listen, and engage with employees rather than waiting for employees to come to them, which fosters open communication, early problem identification, and stronger employee-manager trust. This is the precise and recognized HR/management term for the behavior described in the question.