ATM is a term used in texting slang to say at the moment, basically used to say what something is doing presently or what such a person is feeling. For example, one would reply "I am busy ATM" when asked by a friend what one is doing. This phrase is a typical slang phrase of the texting culture made for easy and quick communication. So next time, if you want to tell what you are doing right now, think about using ATM! If you want to learn more slang you can visit Slang texting dictionary, here you get every slang and short word.