The Collaborative International Dictionary of English v.0.48:

Urgent \Ur"gent\, a. [L. urgens, p. pr. of urgere: cf. F.
   urgent. See Urge.]
   Urging; pressing; besetting; plying, with importunity;
   calling for immediate attention; instantly important. "The
   urgent hour." --Shak.
   [1913 Webster]

         Some urgent cause to ordain the contrary. --Hooker.
   [1913 Webster]

         The Egyptians were urgent upon the people that they
         might send them out of the land in haste. --Ex. xii.
                                                  33.
   [1913 Webster]

WordNet (r) 3.0 (2006):

urgent
    adj 1: compelling immediate action; "too pressing to permit of
           longer delay"; "the urgent words `Hurry! Hurry!'";
           "bridges in urgent need of repair" [syn: pressing,
           urgent]

Moby Thesaurus II by Grady Ward, 1.0:

105 Moby Thesaurus words for "urgent":
   active, actuating, acute, animating, ardent, begging, burning,
   cajoling, causal, causative, choiceless, clamant, clamorous,
   coaxing, compelling, compulsory, critical, crucial, crying,
   cursory, demanding, directive, draining, driving, dunning, earnest,
   emergency, emphatic, energetic, enthusiastic, exacting, exciting,
   exigent, exorbitant, expeditious, extortionate, fervent, festinate,
   feverish, fiery, firm, flying, forceful, furious, glowing,
   grasping, hasty, high-pressure, high-priority, hurried, immediate,
   impassioned, impelling, imperative, imperious, important,
   importunate, impulsive, inducive, insistent, instant, last-minute,
   life-and-death, life-or-death, loud, mandatory, motivating,
   motivational, motive, moving, nagging, necessary, necessitous,
   obligatory, on the spot, passing, passionate, persistent,
   pertinacious, pestering, pivotal, plaguing, pressing, prompt,
   provoking, quick, rush, serious, slap-bang, slapdash, snap,
   solicitous, speedy, stimulating, stirring, superficial, swift,
   taxing, teasing, tenacious, vehement, vital, warm, wheedling,
   without choice