WordNet (r) 3.0 (2006):

rookie
    n 1: an awkward and inexperienced youth [syn: cub,
         greenhorn, rookie]

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "rookie":
   abecedarian, alphabetarian, apprentice, arriviste, articled clerk,
   baby, beginner, boot, catechumen, colt, conscript, deb, debutant,
   draft, drafted man, draftee, emigrant, enlistee, enrollee, entrant,
   fledgling, freshman, gate-crasher, greenhorn, greeny, ignoramus,
   immigrant, inductee, infant, initiate, intruder, learner, levy,
   neophyte, nestling, new arrival, new boy, newcomer, novice,
   novitiate, novus homo, parvenu, postulant, probationer,
   probationist, raw recruit, recruit, selectee, settler, squatter,
   stowaway, tenderfoot, trainee, tyro, upstart