The Collaborative International Dictionary of English v.0.48:

Popular \Pop"u*lar\, a. [L. popularis, fr. populus people: cf.
   F. populaire. See People.]
   1. Of or pertaining to the common people, or to the whole
      body of the people, as distinguished from a select
      portion; as, the popular voice; popular elections.
      "Popular states." --Bacon. "So the popular vote inclines."
      --Milton.
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            The men commonly held in popular estimation are
            greatest at a distance.               --J. H.
                                                  Newman.
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   2. Suitable to common people; easy to be comprehended; not
      abstruse; familiar; plain.
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            Homilies are plain popular instructions. --Hooker.
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   3. Adapted to the means of the common people; possessed or
      obtainable by the many; hence, cheap; common; ordinary;
      inferior; as, popular prices; popular amusements.
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            The smallest figs, called popular figs, . . . are,
            of all others, the basest and of least account.
                                                  --Holland.
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   4. Beloved or approved by the people; pleasing to people in
      general, or to many people; as, a popular preacher; a
      popular law; a popular administration.
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   5. Devoted to the common people; studious of the favor of the
      populace. [R.]
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            Such popular humanity is treason.     --Addison.
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   6. Prevailing among the people; epidemic; as, a popular
      disease. [Obs.] --Johnson.
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   Popular action (Law), an action in which any person may sue
      for penalty imposed by statute. --Blackstone.
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WordNet (r) 3.0 (2006):

popular
    adj 1: regarded with great favor, approval, or affection
           especially by the general public; "a popular tourist
           attraction"; "a popular girl"; "cabbage patch dolls are
           no longer popular" [ant: unpopular]
    2: carried on by or for the people (or citizens) at large; "the
       popular vote"; "popular representation"; "institutions of
       popular government"
    3: representing or appealing to or adapted for the benefit of
       the people at large; "democratic art forms"; "a democratic or
       popular movement"; "popular thought"; "popular science";
       "popular fiction" [syn: democratic, popular]
    4: (of music or art) new and of general appeal (especially among
       young people) [syn: popular, pop]

Moby Thesaurus II by Grady Ward, 1.0:

190 Moby Thesaurus words for "popular":
   Babbittish, Philistine, accepted, accessible, acclaimed,
   accustomed, admired, admitted, adored, advocated, all the rage,
   all the thing, amateur, applauded, approved, associated, average,
   backed, beloved, besetting, bourgeois, campy, celebrated,
   cherished, civil, collective, collectivistic, common, commonplace,
   communal, communistic, commutual, conformable, congregational,
   conjoint, consuetudinary, conventional, cooperative, coveted,
   cried up, current, customary, darling, dear, dearly beloved,
   desired, distinguished, dominant, epidemic, established, esteemed,
   everyday, fabled, famed, familiar, famous, far-famed, far-heard,
   fashionable, favored, favorite, general, generally accepted,
   habitual, held dear, high-camp, highly touted, hip, homely,
   homespun, honored, hoped-for, hot, household, in, in common,
   in demand, in fashion, in favor, in good odor, in style, in vogue,
   inexpensive, joint, kitschy, laic, laical, lay, leading, legendary,
   longed-for, loved, low, low-camp, low-priced, marked, mod, modern,
   much acclaimed, mutual, mythical, new, newfashioned, nonclerical,
   nonecclesiastical, nonministerial, nonordained, nonpastoral,
   nonreligious, normal, normative, notable, noted, notorious,
   obtaining, occupy, of mark, of note, ordinary, pandemic, people,
   pet, plebeian, pop, populate, precious, predominant, predominating,
   preferred, prescribed, prescriptive, prevailing, prevalent, prized,
   prominent, public, rampant, reasonable, received, reciprocal,
   recommended, regnant, regular, regulation, reigning, renowned,
   revered, rife, routine, ruling, running, secular, secularist,
   secularistic, self-governing, set, simplified, smart, social,
   socialistic, societal, standard, stereotyped, stock, stylish,
   supported, talked-about, talked-of, temporal, tenant, time-honored,
   traditional, treasured, trendy, understandable, universal,
   up-to-date, up-to-datish, up-to-the-minute, usual, vernacular,
   vulgar, wanted, well-beloved, well-known, well-liked,
   well-thought-of, widespread, wished-for, wonted