WordNet (r) 3.0 (2006):

ABM
    n 1: a defensive missile designed to shoot down incoming
         intercontinental ballistic missiles; "the Strategic Arms
         Limitation Talks placed limits on the deployment of ABMs"
         [syn: antiballistic missile, ABM]

The Free On-line Dictionary of Computing (19 January 2023):

Asynchronous Balanced Mode
ABM

    A communication mode of HDLC and derivative
   protocols, supporting peer-oriented point-to-point
   communications between two nodes, where either node can
   initiate transmission.

   (1997-05-07)