The Collaborative International Dictionary of English v.0.48:

Fm \Fm\ prop. n.
   The chemical symbol for Fermium, a transuranic element.

   Syn: fermium, atomic number 100.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

FM \FM\ n. [Frequency Modulaiton.]
   A method of transmitting radio signals by modulating the
   frequency of the carrier wave; -- opposed to AM (amplitude
   modulation), in which the signal modulates the amplitude,
   rather than the frequency of the carrier wave. [acron.]

   Syn: frequency modulation.
        [WordNet 1.5 +PJC]

The Collaborative International Dictionary of English v.0.48:

Fm \Fm\ prop. n.
   the symbol for the element Fermium.
   [PJC]

WordNet (r) 3.0 (2006):

FM
    n 1: modulation of the frequency of the (radio) carrier wave
         [syn: frequency modulation, FM]
    2: a radioactive transuranic metallic element produced by
       bombarding plutonium with neutrons [syn: fermium, Fm,
       atomic number 100]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

FM
       Frequenz-Modulation


The Jargon File (version 4.4.7, 29 Dec 2003):

FM
 /F?M/, n.

    1. [common] Not ?Frequency Modulation? but rather an abbreviation for
    ?Fucking Manual?, the back-formation from RTFM. Used to refer to the
    manual itself in the RTFM. ?Have you seen the Networking FM lately??

    2. Abbreviation for ?Fucking Magic?, used in the sense of black magic.


The Free On-line Dictionary of Computing (30 December 2018):

FM

   1.  Frequency Modulation.

   2.  Fucking Manual, a back-formation from RTFM.
   Used to refer to the manual itself.

   3.  Fucking Magic, in the sense of black magic.

   (2001-04-30)


The Free On-line Dictionary of Computing (30 December 2018):

fm

    The country code for the Federated States of
   Micronesia.

   Heavily used for vanity domains by FM radio stations.

   (1999-01-27)