1. atm(n = noun.quantity) atmosphere, standard atmosphere, standard pressure - a unit of pressure: the pressure that will support a column of mercury 760 mm high at sea level and 0 degrees centigrade;
is a kind of pressure unit
has particulars: s.t.p., stp
2. atm(n = noun.communication) asynchronous transfer mode - 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; "ATM is used for both LAN and WAN"
is a kind of data communication, digital communication
3. atm(n = noun.artifact) automated teller, automated teller machine, automatic teller, automatic teller machine, cash dispenser, cash machine - an unattended machine (outside some banks) that dispenses money when a personal coded card is used;
is a kind of machine
atm, abbr. Physics atmosphere(s).