Definitions of Atm:

noun: a means of digital communications that is capable of very high speeds; suitable for transmission of images or voice or video as well as data
Example: "ATM is used for both LAN and WAN"
noun: a unit of pressure: the pressure that will support a column of mercury 760 mm high at sea level and 0 degrees centigrade
noun: an unattended machine (outside some banks) that dispenses money when a personal coded card is used