The Collaborative International Dictionary of English v.0.48:

Apologetics \A*pol`o*get"ics\, n.
   That branch of theology which defends the Holy Scriptures,
   and sets forth the evidence of their divine authority.
   [1913 Webster]

WordNet (r) 3.0 (2006):

apologetics
    n 1: the branch of theology that is concerned with the defense
         of Christian doctrines

Moby Thesaurus II by Grady Ward, 1.0:

57 Moby Thesaurus words for "apologetics":
   Buddhology, Mariolatry, Mariology, Mercersburg theology, apologia,
   apology, argument, argumentation, bicker, bickering, canonics,
   casuistry, contention, controversy, crisis theology, defense,
   dialogical theology, disputation, dispute, divinity, doctrinalism,
   doctrinism, dogmatics, eschatology, existential theology, flyting,
   hagiography, hagiology, hassle, hierology, hubbub, litigation,
   logomachy, logos Christology, logos theology, natural theology,
   neoorthodox theology, neoorthodoxy, paper war, passage of arms,
   patristic theology, phenomenological theology, physicotheology,
   polemic, polemics, rationalism, religion, rhubarb,
   scholastic theology, secularism, set-to, soteriology, systematics,
   theology, verbal engagement, war of words, wrangling