"DialedNumber Recorder". Referenced frequently in HBO's "The Wire", when the cops are talking about getting phone wiretaps on their targets. It records the phone calls that are intercepted.
Get me a DNR on Stringer Bell's cell phone so I can listen to that fucker's calls.
Means "Do Not Rececitate"; slang used when drinking to acknowledge that you are going to drink a heavy load of alcohol and if you stop breathing do not want to be saved; used to speak of others who you wish if on the verge of death would not be revived.
DNR, often called a scratch, in track, refers to instances where an individual withdraws from the race before it begins. Not the same as DQ (or disqualification), in which a runner is removed after the start. Occasionally, in hand-timed races where there are less timers than runners, DNR will be used to indicate that a runner did not finish fast enough to have his/her time recorded.