The Collaborative International Dictionary of English v.0.48:

earlier \earlier\ adj.
   occurring at a prior time; as, on earlier occasions.
   [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Early \Ear"ly\, a. [Compar. Earlier ([~e]r"l[i^]*[~e]r);
   superl. Earliest.] [OE. earlich. [root]204. See Early,
   adv.]
   1. In advance of the usual or appointed time; in good season;
      prior in time; among or near the first; -- opposed to
      late; as, the early bird; an early spring; early fruit.
      [1913 Webster]

            Early and provident fear is the mother of safety.
                                                  --Burke.
      [1913 Webster]

            The doorsteps and threshold with the early grass
            springing up about them.              --Hawthorne.
      [1913 Webster]

   2. Coming in the first part of a period of time, or among the
      first of successive acts, events, etc.
      [1913 Webster]

            Seen in life's early morning sky.     --Keble.
      [1913 Webster]

            The forms of its earlier manhood.     --Longfellow.
      [1913 Webster]

            The earliest poem he composed was in his seventeenth
            summer.                               --J. C.
                                                  Shairp.
      [1913 Webster]

   Early English (Philol.) See the Note under English.

   Early English architecture, the first of the pointed or
      Gothic styles used in England, succeeding the Norman style
      in the 12th and 13th centuries.

   Syn: Forward; timely; not late; seasonable.
        [1913 Webster]

WordNet (r) 3.0 (2006):

earlier
    adv 1: earlier in time; previously; "I had known her before";
           "as I said before"; "he called me the day before but your
           call had come even earlier"; "her parents had died four
           years earlier"; "I mentioned that problem earlier" [syn:
           earlier, before]
    2: comparatives of `soon' or `early'; "Come a little sooner, if
       you can"; "came earlier than I expected" [syn: sooner,
       earlier]
    3: before now; "why didn't you tell me in the first place?"
       [syn: in the first place, earlier, in the beginning,
       to begin with, originally]
    adj 1: (comparative and superlative of `early') more early than;
           most early; "a fashion popular in earlier times"; "his
           earlier work reflects the influence of his teacher";
           "Verdi's earliest and most raucous opera" [syn:
           earlier, earliest]

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "earlier":
   aforetime, already, antecedent, anterior, anticipatory, as yet,
   before, before all, before now, beforehand, beforetime, ci-devant,
   down, early, elder, ere, ere then, erenow, erewhile, erst,
   erstwhile, first, fore, foregoing, former, formerly, heretofore,
   historically, hitherto, in the past, in times past, inferior,
   lower, lowest, nether, older, once, only yesterday, or ever,
   preceding, precurrent, preexistent, prehistorically, previous,
   previously, prime, prior, priorly, recently, senior, so far,
   sooner, subjacent, then, theretofore, thus far, under, whilom,
   yesterday, yet