Found this tonight while doing some preflight:
MSN 08/051 MSN RWY 18/36 RCL NONSTD MARKING BTN TWY A4 AND TWY A5
MSN 08/052 MSN RWY 3/21 RCL NONSTD MARKING BTN TWY B1 AND TWY B2
And I’m not sure why, but RCL took me a few minutes to put together.
RCL = Runway Centerline
So, decoding the above NOTAM. At MSN (Madison, WI) the centerline on runway 18/36 and runway 3/21 has non standard markings between the respective taxiways.
If you have any more questions. You can always download this handy NOTAM Contractions (693) pamphlet which contains the most widely used Notam contractions.