The Collaborative International Dictionary of English v.0.48:

Fo \Fo\ (f[=o]), n.
   The Chinese name of Buddha.
   [1913 Webster]

WordNet (r) 3.0 (2006):

FO
    n 1: an officer holding the rank of major or lieutenant colonel
         or colonel [syn: field-grade officer, field officer,
         FO]

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

fo

    The country code for the Faroe Islands.

   (1999-01-27)