The Collaborative International Dictionary of English v.0.48:

Quarterly \Quar"ter*ly\, a.
   1. Containing, or consisting of, a fourth part; as, quarterly
      seasons.
      [1913 Webster]

   2. Recurring during, or at the end of, each quarter; as,
      quarterly payments of rent; a quarterly meeting.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Quarterly \Quar"ter*ly\, n.; pl. Quarterlies.
   A periodical work published once a quarter, or four times in
   a year.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Quarterly \Quar"ter*ly\, adv.
   1. By quarters; once in a quarter of a year; as, the returns
      are made quarterly.
      [1913 Webster]

   2. (Her.) In quarters, or quarterings; as, to bear arms
      quarterly; in four or more parts; -- said of a shield thus
      divided by lines drawn through it at right angles.
      [1913 Webster]

WordNet (r) 3.0 (2006):

quarterly
    adv 1: in diagonally opposed quarters of an escutcheon; "two
           coats of arms borne quarterly"
    2: in three month intervals; "interest is compounded quarterly"
       [syn: quarterly, every quarter]
    adj 1: of or relating to or consisting of a quarter; "quarterly
           report"
    n 1: a periodical that is published every quarter (or four
         issues per year)

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "quarterly":
   annual, biannual, biennial, bimonthly, biweekly, catamenial,
   centenary, centennial, daily, daybook, decennial, diary, diurnal,
   ephemeris, fortnightly, gazette, hebdomadal, hourly, journal,
   magazine, menstrual, momentary, momently, monthly, newsmagazine,
   organ, periodical, pictorial, quotidian, review, secular,
   semestral, semiannual, semimonthly, semiweekly, semiyearly, serial,
   slick magazine, tertian, trade magazine, triennial, weekly,
   yearbook, yearly