Looking it up, you might mean it glows in some color?
Looking it up, you might mean it glows in some color?
For example, if you take two tables of the same height, and push them together, their surfaces will be "flush".
Or, if something is embedded inside a surface, so that it sits at the same level as the surface. The slot on some optical drives is a good example of a slot that is "flush" [1].
So on an ATM a "flush" slot would be one that is just a plain slot in the flat plastic surface of the ATM, without any anti-skimming device which sticks out the front.
[1] https://www.dataquest.ch/images/uploads/newsimages/9056/usb_...
Are you familiar with poker? We have another use of the word `flush` in that context, https://en.wikipedia.org/wiki/List_of_poker_hands#Flush where all of the cards are the same suit. So it's a similar use of flush in this instance, that everything is the same. It's similar to this thread's use of "flush".
As in, your face will go flush if you realize your credit card reader is not flush because you might have just flushed all your winnings from having a poker flush down the toilet.
To be "flush with money" is to have a lot of money---in poker, to be flush with hearts is to have 5 hearts.
http://www.oed.com/view/Entry/72182?rskey=4UKORw&result=4&is...
http://www.learnersdictionary.com/definition/flush
Scroll down to the 4th listing, which is the adjective version. "even or level with another surface"
So the original poster meant that he thought the card reader should just be completely even or level with the front of the machine. I guess that would just be a plain slot.