An apologist is a person who engages in the study and practice of the intellectual defense of a belief system -- in our case, the Christian faith. The word apologist is derive from the Greek apologia ("defense") and apologia ("to defend").
An apologist is a person who makes an apology, speaks or writes in defense of the faith, and especially a person who argues in defense of Christianity.
Scripture calls each believer to be an apologist. 1Peter 3:15-16 instructs: "Simply proclaim the Lord Christ holy in your hearts, and always have your answer ready for people who ask you the reason for the hope that you have. But give it with courtesy and respect and with a clear conscience, so that those who slander your good behaviour in Christ may be ashamed of their accusations." (New Jerusalem Bible, italics added)
Although anyone who takes the study and practice of apologetics seriously may be called an apologist, some persons are especially gifted and equipped to present arguments in defense of the faith, it is these people that are meant generally as apologists.
Some of the noted Christian apologists of the early centuries are: