antemeridiem

an·te me·rid·i·em (ăn'tē mə-rĭdʹē-əm) adv. & adj. Abbr. A.M. or a.m. or A.M.

Before noon. Used chiefly in the abbreviated form to specify the hour:

10:30 A.M.; an A.M. appointment.

See Usage Note at A.M.

  [Latin ante, before + merīdiem, accusative of merīdiēs, noon.]

* * *