apologist

n. theologian who speaks in defense of Christianity; person who argues in favor of something

Apologists are authors, writers, editors of scientific logs or academic journals, and leaders known for taking on the points in arguments, conflicts or positions that are either placed under popular scrutinies or viewed under persecutory examinations. The term comes from the Greek word apologia (απολογία), meaning defense of a position against an attack.
See more at Wikipedia.org...

Noun
1. a person who argues to defend or justify some policy or institution; "an apologist for capital punishment"
(synonym) vindicator, justifier
(hypernym) advocate, advocator, proponent, exponent

(n.)
One who makes an apology; one who speaks or writes in defense of a faith, a cause, or an institution; especially, one who argues in defense of Christianity.
  

n.
چھما يا معافي چاہنے والا , عذر خواہي کرنا , عفو چاہنا , معافي يا چھما مانگني
to apologize for not answering one's letter
خط کے جواب نہ دينے کا عذر کرنا