There is a great deal of confusion around this question because the term is often defined differently from church to church. There is no clear definition, but there is a clear picture of who the reformers were. The reformers did not call themselves reformers. They simply did the work of asking that most vital question, “what does Scripture have to say about the nature of God and how man is saved through Jesus Christ?”

Reformed Church – Why do we need a label?
We find it helpful to use this distinction in our day and age not as a means for division but for the sake of clarity.
We must not be intellectually lazy, but instead, we are to honor God’s Word well by investing great effort into knowing who God is, how He saves us, and how we are to live with Him.
As a Reformed Church
We believe in the doctrines of grace. Truths that speak of the total depravity of man, the unconditional nature of election, the limited or particular nature of the atonement, the irresistibility of the effectual call, and the perseverance and preservation of the saints. In this ‘Reformed’ tradition are the great names of Church history. John Calvin, John Knox, John Bunyan, John Newton, Matthew Henry, George Whitefield, Jonathan Edwards, Adoniram Judson, William Carey, C.H. Spurgeon, A.W. Pink, and a host of others held tenaciously to the Reformed Faith. We must underscore, however, that we hold to these truths not because Calvin and these other great men of church history held to them but because Jesus and the apostles so clearly taught them. We also must be careful not to interpret Scripture according to our presuppositions but carefully and humbly come to the Bible with our doctrines in open hands, allowing God to have the last say and not our creeds or confessions.
Can I attend your church if I don’t hold to the same doctrines?
Absolutely! While these are foundational to how we interpret the Bible, teach, and counsel, they should not keep us from loving one another. We ask our members to understand what we believe, to not be divisive, to study God’s Word humbly, and to be gracious to one another, but full subscription to our confession is not required.
For a fuller definition of Reformed Baptist beliefs please read this helpful article – What is a Reformed Baptist by Tom Hicks.