John Piper has a great post on the question that I answer at least once per month, if not more. . .
The premise: Instead of saying “yes,” and allowing the generality of the term to linger, tell them what you believe! Here’s the jist:
If they say, “Are you a Calvinist?” say, “You decide. Here is what I believe . . .”
I believe I am so spiritually corrupt and prideful and rebellious that I would never have come to faith in Jesus without God’s merciful, sovereign victory over the last vestiges of my rebellion. (1 Corinthians 2:14; Ephesians 3:1–4; Romans 8:7).
I believe that God chose me to be his child before the foundation of the world, on the basis of nothing in me, foreknown or otherwise. (Ephesians 1:4–6; Acts 13:48; Romans 8:29–30; 11:5–7)
I believe Christ died as a substitute for sinners to provide a bona fide offer of salvation to all people, and that he had an invincible design in his death to obtain his chosen bride, namely, the assembly of all believers, whose names were eternally written in the book of life of the Lamb that was slain. (John 3:16; John 10:15; Ephesians 5:25; Revelation 13:8)
When I was dead in my trespasses, and blind to the beauty of Christ, God made me alive, opened the eyes of my heart, granted me to believe, and united me to Jesus, with all the benefits of forgiveness and justification and eternal life. (Ephesians 2:4–5; 2 Corinthians 4:6; Philippians 2:29; Ephesians 2:8–9; Acts 16:14; Ephesians 1:7; Philippians 3:9)
I am eternally secure not mainly because of anything I did in the past, but decisively because God is faithful to complete the work he began—to sustain my faith, and to keep me from apostasy, and to hold me back from sin that leads to death. (1 Corinthians 1:8–9; 1 Thessalonians 5:23–24; Philippians 1:6; 1 Peter 1:5; Jude 1:25; John 10:28–29; 1 John 5:16)
Read the whole thing here.